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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>python_primer.py</title>
<style>
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}
body { background: var(--bg); color: var(--fg); margin: 0; padding: 16px; font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace; }
pre { background: var(--bg); color: var(--fg); padding: 16px; border-radius: 8px; overflow: auto; line-height: 1.45; font-size: 13px; }
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</style>
</head>
<body>
<pre><code><span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># 1. Getting Started #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># Welcome to the ShwaTech Python Primer!</span>
<span class="tok-comment"># This primer was authored by hand by Christian Holslin and was last updated on February 15, 2026.</span>
<span class="tok-comment"># </span>
<span class="tok-comment"># We will start with the basic syntax of the language and work our way up</span>
<span class="tok-comment"># You will notice these lines that start with a hashtag</span>
<span class="tok-comment"># These are comments in Python, they will be ignored by the interpreter</span>
<span class="tok-comment"># Comments allow you to explain what your code is doing</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Syntax & Scope #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-name">hello_world</span> <span class="tok-operator">=</span> <span class="tok-string">'Hello, world!'</span> <span class="tok-comment"># Python is a script language</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">hello_world</span><span class="tok-punct">)</span> <span class="tok-comment"># Each line is an instruction to the interpreter</span>
<span class="tok-comment"># Python allows you to combine instructions onto a single line using the ; operator</span>
<span class="tok-name">hello_world</span> <span class="tok-operator">=</span> <span class="tok-string">'Hello again, world!'</span><span class="tok-punct">;</span> <span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">hello_world</span><span class="tok-punct">)</span>
<span class="tok-comment"># Python allows you to carry instructions onto subsequent lines with the \ operator</span>
<span class="tok-name">hello_world</span> <span class="tok-operator">=</span> \
<span class="tok-string">'Hello again there, world!'</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">hello_world</span><span class="tok-punct">)</span>
<span class="tok-comment"># Scope in Python is defined by indentation</span>
<span class="tok-name">the_number_seven</span> <span class="tok-operator">=</span> <span class="tok-number">7</span> <span class="tok-comment"># This is at the top scope</span>
<span class="tok-keyword">if</span> <span class="tok-name">the_number_seven</span> <span class="tok-operator">!=</span> <span class="tok-number">7</span><span class="tok-punct">:</span> <span class="tok-comment"># Conditional scopes like ifs...</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'Oops!'</span><span class="tok-punct">)</span> <span class="tok-comment"># Get indented with tab or spaces</span>
<span class="tok-comment"># Function variables do not persist outside of the function scope</span>
<span class="tok-keyword">def</span> <span class="tok-name">do_math</span><span class="tok-punct">(</span><span class="tok-operator">*</span><span class="tok-name">a</span><span class="tok-punct">)</span><span class="tok-punct">:</span>
<span class="tok-name">math_result</span> <span class="tok-operator">=</span> <span class="tok-builtin">sum</span><span class="tok-punct">(</span><span class="tok-name">a</span><span class="tok-punct">)</span> <span class="tok-comment"># math_result goes out of scope after the function call</span>
<span class="tok-keyword">return</span> <span class="tok-name">math_result</span> <span class="tok-comment"># Therefore we must return it to the caller</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Namespaces & External References #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python defines everything you do in your base script as the local namespace</span>
<span class="tok-name">i_like_bacon</span> <span class="tok-operator">=</span> <span class="tok-keyword">True</span> <span class="tok-comment"># i_like_bacon is defined in the local namespace</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">i_like_bacon</span><span class="tok-punct">)</span> <span class="tok-comment"># So we can pass it to print as-is</span>
<span class="tok-comment"># When you import a module it gets assigned a namespace name</span>
<span class="tok-keyword">import</span> <span class="tok-name">math</span> <span class="tok-comment"># Here we import the math module which keeps the same namespace name</span>
<span class="tok-name">math</span><span class="tok-punct">.</span><span class="tok-name">sqrt</span><span class="tok-punct">(</span><span class="tok-number">654.23</span><span class="tok-punct">)</span> <span class="tok-comment"># Then we use the math namespace to call the sqrt function</span>
<span class="tok-comment"># sqrt() is not a method because math is a namespace, not an object</span>
<span class="tok-comment"># You can also alias the import of a module to avoid collisions</span>
<span class="tok-keyword">import</span> <span class="tok-name">statistics</span> <span class="tok-keyword">as</span> <span class="tok-name">stat_man</span> <span class="tok-comment"># Here we import statistics with the alias stat_man</span>
<span class="tok-name">stat_man</span><span class="tok-punct">.</span><span class="tok-name">mean</span><span class="tok-punct">(</span><span class="tok-punct">[</span><span class="tok-number">1</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">3</span><span class="tok-punct">,</span><span class="tok-number">4</span><span class="tok-punct">,</span><span class="tok-number">4</span><span class="tok-punct">,</span><span class="tok-number">4</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-number">6</span><span class="tok-punct">,</span><span class="tok-number">7</span><span class="tok-punct">,</span><span class="tok-number">7</span><span class="tok-punct">,</span><span class="tok-number">7</span><span class="tok-punct">,</span><span class="tok-number">7</span><span class="tok-punct">,</span><span class="tok-number">8</span><span class="tok-punct">,</span><span class="tok-number">8</span><span class="tok-punct">]</span><span class="tok-punct">)</span> <span class="tok-comment"># We can call statistics functions with the stat_man prefix</span>
<span class="tok-comment"># Importing with the from keyword imports functions into the local namespace</span>
<span class="tok-comment"># Importing using from can be limited or unlimited in scope</span>
<span class="tok-keyword">from</span> <span class="tok-name">base64</span> <span class="tok-keyword">import</span> <span class="tok-operator">*</span> <span class="tok-comment"># This imports everything from the base64 module into the local namespace</span>
<span class="tok-comment"># Generally you would avoid doing this because it's almost always unnecessary</span>
<span class="tok-keyword">from</span> <span class="tok-name">json</span> <span class="tok-keyword">import</span> <span class="tok-name">dumps</span> <span class="tok-comment"># This imports only the dumps function from the json module</span>
<span class="tok-name">dumps</span><span class="tok-punct">(</span><span class="tok-punct">[</span><span class="tok-number">1</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">3</span><span class="tok-punct">,</span><span class="tok-number">4</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">]</span><span class="tok-punct">)</span> <span class="tok-comment"># When you import a single function from a module it gets loaded into the local namespace</span>
<span class="tok-keyword">from</span> <span class="tok-name">json</span> <span class="tok-keyword">import</span> <span class="tok-name">dumps</span> <span class="tok-keyword">as</span> <span class="tok-name">convert_to_json</span> <span class="tok-comment"># As such, individual functions imported into the local</span>
<span class="tok-name">convert_to_json</span><span class="tok-punct">(</span><span class="tok-punct">[</span><span class="tok-number">1</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">3</span><span class="tok-punct">,</span><span class="tok-number">4</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">]</span><span class="tok-punct">)</span> <span class="tok-comment"># namespace can also be aliased to avoid conflicts</span>
<span class="tok-keyword">from</span> <span class="tok-name">json</span> <span class="tok-keyword">import</span> <span class="tok-name">load</span><span class="tok-punct">,</span> <span class="tok-name">detect_encoding</span> <span class="tok-comment"># You can import multiple items with a single import statement</span>
<span class="tok-comment"># Python scripts in the same directory can be imported using their filename without the file extension</span>
<span class="tok-keyword">from</span> <span class="tok-name">python_primer_refs</span> <span class="tok-keyword">import</span> <span class="tok-name">three_blind_mice</span> <span class="tok-comment"># This is python_primer_ref.py in the current directory</span>
<span class="tok-name">three_blind_mice</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># We can import this function into the local namespace and call it</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Variables, Functions & Methods #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># A variable is a name to which you assign a value using the assignment (=) operator</span>
<span class="tok-name">my_variable</span> <span class="tok-operator">=</span> <span class="tok-string">'Christian'</span>
<span class="tok-comment"># Variables cannot start with a number or token, they should generally start with a letter</span>
<span class="tok-name">one_more_time</span> <span class="tok-operator">=</span> <span class="tok-string">'One More Time'</span> <span class="tok-comment"># This is legal</span>
<span class="tok-comment"># 1_more_time = 'illegal' # This is illegal, so we commented it out</span>
<span class="tok-comment"># $_in_pocket = 42.50 # This is also illegal</span>
<span class="tok-comment"># Variables declared at lower scopes persist at higher scopes</span>
<span class="tok-name">the_number_eight</span> <span class="tok-operator">=</span> <span class="tok-number">8</span> <span class="tok-comment"># Here we declare the_number_eight</span>
<span class="tok-keyword">if</span> <span class="tok-name">the_number_eight</span> <span class="tok-operator">==</span> <span class="tok-number">8</span><span class="tok-punct">:</span> <span class="tok-comment">#</span>
<span class="tok-name">the_number_nine</span> <span class="tok-operator">=</span> <span class="tok-number">9</span> <span class="tok-comment"># Here we declare the_number_nine inside an if scope</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'The number nine is:'</span><span class="tok-punct">,</span><span class="tok-name">the_number_nine</span><span class="tok-punct">)</span> <span class="tok-comment"># After the if we can still access the_number_nine</span>
<span class="tok-comment"># This, however, does not apply to function scopes</span>
<span class="tok-keyword">def</span> <span class="tok-name">goes_out_of_scope</span><span class="tok-punct">(</span><span class="tok-name">my_name</span><span class="tok-punct">)</span><span class="tok-punct">:</span>
<span class="tok-name">also_my_name</span> <span class="tok-operator">=</span> <span class="tok-name">my_name</span>
<span class="tok-comment"># print(also_my_name) # also_my_name does out of scope because it was declared in a function scope</span>
<span class="tok-comment"># Functions are invoked using parenthesis like this</span>
<span class="tok-builtin">sum</span><span class="tok-punct">(</span> <span class="tok-punct">[</span><span class="tok-number">3</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">7</span><span class="tok-punct">]</span> <span class="tok-punct">)</span> <span class="tok-comment"># Calculates the sum of the numbers in the List</span>
<span class="tok-comment"># sum() is called a built-in function</span>
<span class="tok-comment"># Functions that are part of an object are called methods, they are invoked with the dot (.) operator</span>
<span class="tok-punct">[</span><span class="tok-number">3</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">7</span><span class="tok-punct">]</span><span class="tok-punct">.</span><span class="tok-name">append</span><span class="tok-punct">(</span><span class="tok-number">4</span><span class="tok-punct">)</span> <span class="tok-comment"># Calling the append() method on a List literal</span>
<span class="tok-string">'Hello, {}!'</span><span class="tok-punct">.</span><span class="tok-builtin">format</span><span class="tok-punct">(</span><span class="tok-string">'world'</span><span class="tok-punct">)</span> <span class="tok-comment"># Calling the format() method on a String literal</span>
<span class="tok-name">one_more_time</span><span class="tok-punct">.</span><span class="tok-name">count</span><span class="tok-punct">(</span><span class="tok-string">'One'</span><span class="tok-punct">)</span> <span class="tok-comment"># Calling the count() method on a String variable</span>
<span class="tok-comment"># Variables can be assigned and reassigned to any value at run-time regardless of type</span>
<span class="tok-name">some_thing</span> <span class="tok-operator">=</span> <span class="tok-number">12</span>
<span class="tok-name">some_thing</span> <span class="tok-operator">=</span> <span class="tok-string">'Twelve'</span>
<span class="tok-name">some_thing</span> <span class="tok-operator">=</span> <span class="tok-number">7.5</span>
<span class="tok-name">some_thing</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-number">1</span><span class="tok-punct">,</span><span class="tok-number">1</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">3</span><span class="tok-punct">,</span><span class="tok-number">4</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">]</span>
<span class="tok-name">some_thing</span> <span class="tok-operator">=</span> <span class="tok-builtin">range</span><span class="tok-punct">(</span><span class="tok-number">9</span><span class="tok-punct">)</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Primitives & Literals #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># A primitive or literal in Python is a static value specified directly, such as the following:</span>
<span class="tok-name">my_name</span> <span class="tok-operator">=</span> <span class="tok-string">'Christian Holslin'</span> <span class="tok-comment"># String literal (word or words in single quotes)</span>
<span class="tok-name">my_company</span> <span class="tok-operator">=</span> <span class="tok-string">"ShwaTech LLC"</span> <span class="tok-comment"># String literal (word or words in double quotes)</span>
<span class="tok-name">my_age</span> <span class="tok-operator">=</span> <span class="tok-number">43</span> <span class="tok-comment"># Integer literal</span>
<span class="tok-name">my_favorite_number</span> <span class="tok-operator">=</span> <span class="tok-number">7.0</span> <span class="tok-comment"># Float literal</span>
<span class="tok-name">am_i_awesome</span> <span class="tok-operator">=</span> <span class="tok-keyword">True</span> <span class="tok-comment"># Boolean literal (True/False)</span>
<span class="tok-name">this_is_null</span> <span class="tok-operator">=</span> <span class="tok-keyword">None</span> <span class="tok-comment"># Null (Unassigned) literal</span>
<span class="tok-comment"># Multiline String literal, below</span>
<span class="tok-name">my_life_story</span> <span class="tok-operator">=</span> <span class="tok-string">"""
A long, long time ago...
In an In'N'Out Burger far far away...
"""</span>
<span class="tok-comment"># Python supports escape sequences in String literals</span>
<span class="tok-string">'\n'</span> <span class="tok-comment"># Newline</span>
<span class="tok-string">'\t'</span> <span class="tok-comment"># Tab</span>
<span class="tok-string">'\"'</span> <span class="tok-comment"># Double Quotation Mark</span>
<span class="tok-string">'\''</span> <span class="tok-comment"># Single Quotation Mark</span>
<span class="tok-comment"># Python supports collection literals of four (4) different built-in types</span>
<span class="tok-name">my_parents</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-string">'Mom'</span><span class="tok-punct">,</span><span class="tok-string">'Dad'</span><span class="tok-punct">]</span> <span class="tok-comment"># List (indexable & iterable)</span>
<span class="tok-name">my_hobbies</span> <span class="tok-operator">=</span> <span class="tok-punct">(</span><span class="tok-string">'Golf'</span><span class="tok-punct">,</span><span class="tok-string">'Motorcycles'</span><span class="tok-punct">)</span> <span class="tok-comment"># Tuple (immutable, indexable & iterable)</span>
<span class="tok-name">my_friends</span> <span class="tok-operator">=</span> <span class="tok-punct">{</span><span class="tok-string">'Alice'</span><span class="tok-punct">:</span><span class="tok-number">29</span><span class="tok-punct">,</span><span class="tok-string">'Bob'</span><span class="tok-punct">:</span><span class="tok-number">41</span><span class="tok-punct">}</span> <span class="tok-comment"># Dictionary (key/value pairs, all keys must be unique)</span>
<span class="tok-name">my_skills</span> <span class="tok-operator">=</span> <span class="tok-punct">{</span><span class="tok-string">'Python'</span><span class="tok-punct">,</span><span class="tok-string">'C'</span><span class="tok-punct">,</span><span class="tok-string">'C++'</span><span class="tok-punct">,</span><span class="tok-string">'C#'</span><span class="tok-punct">}</span> <span class="tok-comment"># Set (immutable + all items MUST be unique)</span>
<span class="tok-comment"># Collection literals can be combined into complex collections</span>
<span class="tok-name">my_parents</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-punct">{</span><span class="tok-string">'Mom'</span><span class="tok-punct">:</span><span class="tok-string">'Alice'</span><span class="tok-punct">,</span><span class="tok-string">'Age'</span><span class="tok-punct">:</span><span class="tok-number">65</span><span class="tok-punct">}</span><span class="tok-punct">,</span><span class="tok-punct">{</span><span class="tok-string">'Dad'</span><span class="tok-punct">:</span><span class="tok-string">'Bob'</span><span class="tok-punct">,</span><span class="tok-string">'Age'</span><span class="tok-punct">:</span><span class="tok-number">67</span><span class="tok-punct">}</span><span class="tok-punct">]</span> <span class="tok-comment"># List of Dictionaries</span>
<span class="tok-name">my_parents</span> <span class="tok-operator">=</span> <span class="tok-punct">{</span><span class="tok-string">'Mom'</span><span class="tok-punct">:</span><span class="tok-punct">[</span><span class="tok-string">'Alice'</span><span class="tok-punct">,</span><span class="tok-number">65</span><span class="tok-punct">]</span><span class="tok-punct">,</span><span class="tok-string">'Dad'</span><span class="tok-punct">:</span><span class="tok-punct">[</span><span class="tok-string">'Bob'</span><span class="tok-punct">,</span><span class="tok-number">67</span><span class="tok-punct">]</span><span class="tok-punct">}</span> <span class="tok-comment"># Dictionary of Lists</span>
<span class="tok-comment"># Not all combinations are compatible</span>
<span class="tok-comment"># You cannot create a Set of Lists or Dictionaries because neither a List nor Dictionary can be hashed</span>
<span class="tok-comment"># my_skills = {['Python','C','C++','C#'],['Cooking','Baking','Sauce Prep']}</span>
<span class="tok-comment"># my_skills = {{'Mom':'Alice','Age':65},{'Dad':'Bob','Age':67}}</span>
<span class="tok-comment"># But you can create a Set of Tuples</span>
<span class="tok-name">my_skills</span> <span class="tok-operator">=</span> <span class="tok-punct">{</span><span class="tok-punct">(</span><span class="tok-string">'Python'</span><span class="tok-punct">,</span><span class="tok-string">'C'</span><span class="tok-punct">,</span><span class="tok-string">'C++'</span><span class="tok-punct">,</span><span class="tok-string">'C#'</span><span class="tok-punct">)</span><span class="tok-punct">,</span><span class="tok-punct">(</span><span class="tok-string">'Cooking'</span><span class="tok-punct">,</span><span class="tok-string">'Baking'</span><span class="tok-punct">,</span><span class="tok-string">'Sauce Prep'</span><span class="tok-punct">)</span><span class="tok-punct">}</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Arithmetic #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Common arithmetic operators include</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">1</span> <span class="tok-operator">+</span> <span class="tok-number">1</span> <span class="tok-comment"># Addition</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">1</span> <span class="tok-operator">-</span> <span class="tok-number">1</span> <span class="tok-comment"># Subtraction</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">1</span> <span class="tok-operator">*</span> <span class="tok-number">1</span> <span class="tok-comment"># Multiplication</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">1</span> <span class="tok-operator">/</span> <span class="tok-number">1</span> <span class="tok-comment"># Division</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">1</span> <span class="tok-operator">%</span> <span class="tok-number">1</span> <span class="tok-comment"># Modulo</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">1</span> <span class="tok-operator">**</span> <span class="tok-number">1</span> <span class="tok-comment"># Exponentiation</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">1</span> <span class="tok-operator">//</span> <span class="tok-number">1</span> <span class="tok-comment"># Division with Floor</span>
<span class="tok-comment"># The Python interpreter obeys PEMDAS</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">2</span> <span class="tok-operator">*</span> <span class="tok-punct">(</span><span class="tok-number">2</span> <span class="tok-operator">+</span> <span class="tok-number">2</span><span class="tok-punct">)</span> <span class="tok-operator">+</span> <span class="tok-number">2</span> <span class="tok-operator">+</span> <span class="tok-number">2</span> <span class="tok-operator">-</span> <span class="tok-number">2</span> <span class="tok-operator">*</span> <span class="tok-number">2</span> <span class="tok-operator">/</span> <span class="tok-number">2</span> <span class="tok-operator">**</span> <span class="tok-number">2</span> <span class="tok-comment"># This operation</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">2</span> <span class="tok-operator">*</span> <span class="tok-number">4</span> <span class="tok-operator">+</span> <span class="tok-number">2</span> <span class="tok-operator">+</span> <span class="tok-number">2</span> <span class="tok-operator">-</span> <span class="tok-number">2</span> <span class="tok-operator">*</span> <span class="tok-number">2</span> <span class="tok-operator">/</span> <span class="tok-number">2</span> <span class="tok-operator">**</span> <span class="tok-number">2</span> <span class="tok-comment"># Simplfies to this</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">8</span> <span class="tok-operator">+</span> <span class="tok-number">2</span> <span class="tok-operator">+</span> <span class="tok-number">2</span> <span class="tok-operator">-</span> <span class="tok-number">2</span> <span class="tok-operator">*</span> <span class="tok-number">2</span> <span class="tok-operator">/</span> <span class="tok-number">2</span> <span class="tok-operator">**</span> <span class="tok-number">2</span> <span class="tok-comment"># Which simplifies to this</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">12</span> <span class="tok-operator">-</span> <span class="tok-number">2</span> <span class="tok-operator">*</span> <span class="tok-number">2</span> <span class="tok-operator">/</span> <span class="tok-number">2</span> <span class="tok-operator">**</span> <span class="tok-number">2</span> <span class="tok-comment"># Which simplifies to this</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">12</span> <span class="tok-operator">-</span> <span class="tok-number">2</span> <span class="tok-operator">*</span> <span class="tok-number">2</span> <span class="tok-operator">/</span> <span class="tok-number">4</span> <span class="tok-comment"># Which simplifies to...</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">12</span> <span class="tok-operator">-</span> <span class="tok-number">4</span> <span class="tok-operator">/</span> <span class="tok-number">4</span> <span class="tok-comment"># Which simplifies to...</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">12</span> <span class="tok-operator">-</span> <span class="tok-number">1</span> <span class="tok-comment"># Which becomes...</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">11</span> <span class="tok-comment"># x = 11</span>
<span class="tok-comment"># Division will cause the expression to become a float</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Random Numbers #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python includes a random module with generators for random umbers</span>
<span class="tok-keyword">import</span> <span class="tok-name">random</span>
<span class="tok-name">random</span><span class="tok-punct">.</span><span class="tok-name">choice</span><span class="tok-punct">(</span><span class="tok-punct">[</span><span class="tok-number">1</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">3</span><span class="tok-punct">,</span><span class="tok-number">4</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-number">6</span><span class="tok-punct">]</span><span class="tok-punct">)</span> <span class="tok-comment"># Choice picks a random item from the list</span>
<span class="tok-name">random</span><span class="tok-punct">.</span><span class="tok-name">randint</span><span class="tok-punct">(</span><span class="tok-number">0</span><span class="tok-punct">,</span><span class="tok-number">99</span><span class="tok-punct">)</span> <span class="tok-comment"># Randint creates a random number between a and b</span>
<span class="tok-comment"># This List comprehension fills a List with 1000 random integers between 0 and 99999</span>
<span class="tok-name">random_numbers</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-name">random</span><span class="tok-punct">.</span><span class="tok-name">randint</span><span class="tok-punct">(</span><span class="tok-number">0</span><span class="tok-punct">,</span><span class="tok-number">99999</span><span class="tok-punct">)</span> <span class="tok-keyword">for</span> <span class="tok-name">n</span> <span class="tok-keyword">in</span> <span class="tok-builtin">range</span><span class="tok-punct">(</span><span class="tok-number">1000</span><span class="tok-punct">)</span><span class="tok-punct">]</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Boolean Logic #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python supports standard arithmetic boolean comparion operators</span>
<span class="tok-number">5</span> <span class="tok-operator">==</span> <span class="tok-number">1</span> <span class="tok-comment"># Equality</span>
<span class="tok-number">5</span> <span class="tok-operator">></span> <span class="tok-number">1</span> <span class="tok-comment"># Greater than</span>
<span class="tok-number">5</span> <span class="tok-operator"><</span> <span class="tok-number">1</span> <span class="tok-comment"># Less than</span>
<span class="tok-number">5</span> <span class="tok-operator"><=</span> <span class="tok-number">5</span> <span class="tok-comment"># Less than or equal</span>
<span class="tok-number">5</span> <span class="tok-operator">>=</span> <span class="tok-number">5</span> <span class="tok-comment"># Greater than or equal</span>
<span class="tok-number">5</span> <span class="tok-operator">!=</span> <span class="tok-number">5</span> <span class="tok-comment"># Not equal</span>
<span class="tok-comment"># Python supports standard boolean logic operators and, or and not</span>
<span class="tok-punct">(</span><span class="tok-number">2</span> <span class="tok-operator"><</span> <span class="tok-number">3</span><span class="tok-punct">)</span> <span class="tok-keyword">and</span> <span class="tok-punct">(</span><span class="tok-number">5</span> <span class="tok-operator"><</span> <span class="tok-number">4</span><span class="tok-punct">)</span> <span class="tok-comment"># x is False</span>
<span class="tok-punct">(</span><span class="tok-number">2</span> <span class="tok-operator"><</span> <span class="tok-number">3</span><span class="tok-punct">)</span> <span class="tok-keyword">or</span> <span class="tok-punct">(</span><span class="tok-number">5</span> <span class="tok-operator"><</span> <span class="tok-number">4</span><span class="tok-punct">)</span> <span class="tok-comment"># x is True</span>
<span class="tok-keyword">not</span> <span class="tok-punct">(</span><span class="tok-number">2</span> <span class="tok-operator"><</span> <span class="tok-number">3</span><span class="tok-punct">)</span> <span class="tok-comment"># x is False</span>
<span class="tok-comment"># Comparison operators work on primitives and collections</span>
<span class="tok-number">5</span> <span class="tok-operator">==</span> <span class="tok-number">5</span> <span class="tok-comment"># Compare two Ints</span>
<span class="tok-string">'Christian'</span> <span class="tok-operator">==</span> <span class="tok-string">'Peter'</span> <span class="tok-comment"># Compare two Strings</span>
<span class="tok-punct">[</span><span class="tok-string">'a'</span><span class="tok-punct">,</span><span class="tok-string">'b'</span><span class="tok-punct">]</span> <span class="tok-operator">==</span> <span class="tok-punct">[</span><span class="tok-string">'a'</span><span class="tok-punct">,</span><span class="tok-string">'b'</span><span class="tok-punct">]</span> <span class="tok-comment"># Compare two Lists</span>
<span class="tok-punct">(</span><span class="tok-string">'a'</span><span class="tok-punct">,</span><span class="tok-string">'b'</span><span class="tok-punct">)</span> <span class="tok-operator">==</span> <span class="tok-punct">(</span><span class="tok-string">'a'</span><span class="tok-punct">,</span><span class="tok-string">'b'</span><span class="tok-punct">)</span> <span class="tok-comment"># Compare two Tuples</span>
<span class="tok-comment"># String comparisons are case-sensitive</span>
<span class="tok-string">'Christian'</span> <span class="tok-operator">==</span> <span class="tok-string">'cHrisTian'</span> <span class="tok-comment"># This is False</span>
<span class="tok-string">'Christian'</span> <span class="tok-operator">==</span> <span class="tok-string">'Christian'</span> <span class="tok-comment"># This is True</span>
<span class="tok-comment"># Boolean expressions are evaluted conditionally from left to right</span>
<span class="tok-name">empty_list</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-punct">]</span>
<span class="tok-keyword">if</span> <span class="tok-builtin">len</span><span class="tok-punct">(</span><span class="tok-name">empty_list</span><span class="tok-punct">)</span> <span class="tok-operator">></span> <span class="tok-number">0</span> <span class="tok-keyword">and</span> <span class="tok-name">empty_list</span><span class="tok-punct">[</span><span class="tok-number">0</span><span class="tok-punct">]</span> <span class="tok-operator">%</span> <span class="tok-number">2</span> <span class="tok-operator">==</span> <span class="tok-number">0</span><span class="tok-punct">:</span> <span class="tok-comment"># There are two Boolean expressions here.</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'empty_list should be empty'</span><span class="tok-punct">)</span> <span class="tok-comment"># empty_list[0] is normally illegal, but because</span>
<span class="tok-comment"># the first expression is False and the condition is</span>
<span class="tok-comment"># 'and' then the right-hand expression is not</span>
<span class="tok-comment"># evaluated, avoiding an IndexError</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># 2. Basic Operations #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># String Manipulation #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python allows you to combine strings together with concatenation</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-string">'Christian'</span> <span class="tok-operator">+</span> <span class="tok-string">' Holslin'</span> <span class="tok-comment"># Concatenante two Strings</span>
<span class="tok-name">x</span> <span class="tok-operator">+=</span> <span class="tok-string">' is awesome'</span> <span class="tok-comment"># Append a String to a String</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-string">'Christian'</span><span class="tok-punct">.</span><span class="tok-name">join</span><span class="tok-punct">(</span><span class="tok-punct">[</span><span class="tok-string">'Holslin'</span><span class="tok-punct">]</span><span class="tok-punct">)</span> <span class="tok-comment"># Append a List of Strings using the first String as the delimiter</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-string">'.'</span><span class="tok-punct">.</span><span class="tok-name">join</span><span class="tok-punct">(</span><span class="tok-punct">[</span><span class="tok-string">'a'</span><span class="tok-punct">,</span><span class="tok-string">'b'</span><span class="tok-punct">,</span><span class="tok-string">'c'</span><span class="tok-punct">]</span><span class="tok-punct">)</span> <span class="tok-comment"># Results in 'a.b.c'</span>
<span class="tok-comment"># Python has a syntax called f strings which are formatted strings</span>
<span class="tok-name">cash_on_hand</span> <span class="tok-operator">=</span> <span class="tok-number">32.75</span> <span class="tok-comment"># Using a variable...</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span>f'You have $<span class="tok-punct">{</span><span class="tok-name">cash_on_hand</span><span class="tok-punct">}</span> cash on hand.'<span class="tok-punct">)</span> <span class="tok-comment"># embed that variable's value into a string using curly braces</span>
<span class="tok-comment"># Python strings are Lists of characters, they are iterable and can be indexed</span>
<span class="tok-name">my_name</span> <span class="tok-operator">=</span> <span class="tok-string">'Christian'</span> <span class="tok-comment"># Here is my first name</span>
<span class="tok-name">my_name_len</span> <span class="tok-operator">=</span> <span class="tok-builtin">len</span><span class="tok-punct">(</span><span class="tok-name">my_name</span><span class="tok-punct">)</span> <span class="tok-comment"># Get the length of my_name</span>
<span class="tok-name">my_first_initial</span> <span class="tok-operator">=</span> <span class="tok-name">my_name</span><span class="tok-punct">[</span><span class="tok-number">0</span><span class="tok-punct">]</span> <span class="tok-comment"># Index the first letter for my first initial</span>
<span class="tok-name">my_nick_name</span> <span class="tok-operator">=</span> <span class="tok-name">my_name</span><span class="tok-punct">[</span><span class="tok-number">0</span><span class="tok-punct">:</span><span class="tok-number">5</span><span class="tok-punct">]</span> <span class="tok-comment"># Slice the first 5 letters for my nickname</span>
<span class="tok-name">jibberish</span> <span class="tok-operator">=</span> <span class="tok-name">my_name</span><span class="tok-punct">[</span><span class="tok-operator">-</span><span class="tok-number">5</span><span class="tok-punct">:</span><span class="tok-operator">-</span><span class="tok-number">1</span><span class="tok-punct">]</span> <span class="tok-comment"># Negative indeces also work on strings</span>
<span class="tok-keyword">for</span> <span class="tok-name">letter</span> <span class="tok-keyword">in</span> <span class="tok-name">my_name</span><span class="tok-punct">:</span> <span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">letter</span><span class="tok-punct">)</span> <span class="tok-comment"># Iterate the characters in my name</span>
<span class="tok-name">my_list</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-punct">]</span> <span class="tok-comment"># Make an empty List</span>
<span class="tok-name">my_list</span> <span class="tok-operator">+=</span> <span class="tok-name">my_name</span> <span class="tok-comment"># Each letter in my name is added as an item in this List</span>
<span class="tok-name">fav_quote</span> <span class="tok-operator">=</span> <span class="tok-string">"\"Elementary, my dear.\""</span> <span class="tok-comment"># Escape special characters with '\'</span>
<span class="tok-builtin">list</span><span class="tok-punct">(</span><span class="tok-builtin">map</span><span class="tok-punct">(</span><span class="tok-keyword">lambda</span> <span class="tok-name">x</span><span class="tok-punct">:</span> <span class="tok-name">x</span><span class="tok-punct">.</span><span class="tok-name">upper</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">,</span> <span class="tok-string">'test'</span><span class="tok-punct">)</span><span class="tok-punct">)</span> <span class="tok-comment"># Strings can be mapped because they are iterable</span>
<span class="tok-string">'Chris'</span> <span class="tok-keyword">in</span> <span class="tok-name">my_name</span> <span class="tok-comment"># The in operator will test for a substring</span>
<span class="tok-comment"># Python strings are immutable, so changes are illegal</span>
<span class="tok-comment"># my_name[0] = 'F' # This throws a TypeError</span>
<span class="tok-comment"># Python has methods for strings which perform actions on the string itself</span>
<span class="tok-string">'Hello, world!'</span><span class="tok-punct">.</span><span class="tok-name">find</span><span class="tok-punct">(</span><span class="tok-string">'world'</span><span class="tok-punct">)</span> <span class="tok-comment"># Find locates the index of a substring in a String</span>
<span class="tok-string">'{}, {}!'</span><span class="tok-punct">.</span><span class="tok-builtin">format</span><span class="tok-punct">(</span><span class="tok-string">'Hello'</span><span class="tok-punct">,</span><span class="tok-string">'world'</span><span class="tok-punct">)</span> <span class="tok-comment"># Format creates a 'formatted' string => 'Hello, world!'</span>
<span class="tok-string">':'</span><span class="tok-punct">.</span><span class="tok-name">join</span><span class="tok-punct">(</span><span class="tok-punct">[</span><span class="tok-string">'hello'</span><span class="tok-punct">,</span><span class="tok-string">'world'</span><span class="tok-punct">]</span><span class="tok-punct">)</span> <span class="tok-comment"># Join a List with a delimiter into a String => 'hello:world'</span>
<span class="tok-string">'Hello World'</span><span class="tok-punct">.</span><span class="tok-name">lower</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Lower converts all letters to lowercase</span>
<span class="tok-string">'Hello, world!'</span><span class="tok-punct">.</span><span class="tok-name">replace</span><span class="tok-punct">(</span><span class="tok-string">'l'</span><span class="tok-punct">,</span><span class="tok-string">'f'</span><span class="tok-punct">)</span> <span class="tok-comment"># Replace replaces part of a String with another String</span>
<span class="tok-string">'sauce cheese pesto'</span><span class="tok-punct">.</span><span class="tok-name">split</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Split breaks a string into a List using spaces as the delimeter</span>
<span class="tok-string">'sauce:cheese:pesto'</span><span class="tok-punct">.</span><span class="tok-name">split</span><span class="tok-punct">(</span><span class="tok-string">':'</span><span class="tok-punct">)</span> <span class="tok-comment"># Split accepts a delimiter to break a String into a List</span>
<span class="tok-string">' Hello, world! '</span><span class="tok-punct">.</span><span class="tok-name">strip</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Strip removes whitespace at the beginning and end of a string</span>
<span class="tok-string">'*Hello, world!*'</span><span class="tok-punct">.</span><span class="tok-name">strip</span><span class="tok-punct">(</span><span class="tok-string">'*'</span><span class="tok-punct">)</span> <span class="tok-comment"># Strip also accepts a String for leading and trailing removal</span>
<span class="tok-string">'enterprise architect'</span><span class="tok-punct">.</span><span class="tok-name">title</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Title creates a Title Case string => 'Enterprise Architect'</span>
<span class="tok-string">'Hello World'</span><span class="tok-punct">.</span><span class="tok-name">upper</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Upper converts all letters to UPPERCASE</span>
<span class="tok-comment"># Python string formatting supports keyword parameters</span>
<span class="tok-keyword">def</span> <span class="tok-name">email_signature</span><span class="tok-punct">(</span><span class="tok-name">n</span><span class="tok-punct">,</span><span class="tok-name">t</span><span class="tok-punct">,</span><span class="tok-name">pn</span><span class="tok-punct">)</span><span class="tok-punct">:</span>
<span class="tok-keyword">return</span> <span class="tok-string">'{name}, {title} ({phone_number})'</span><span class="tok-punct">.</span><span class="tok-builtin">format</span><span class="tok-punct">(</span><span class="tok-name">name</span><span class="tok-operator">=</span><span class="tok-name">n</span><span class="tok-punct">,</span><span class="tok-name">title</span><span class="tok-operator">=</span><span class="tok-name">t</span><span class="tok-punct">,</span><span class="tok-name">phone_number</span><span class="tok-operator">=</span><span class="tok-name">pn</span><span class="tok-punct">)</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># List Operations #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python Lists are dynamic collections of any item</span>
<span class="tok-name">backpack</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-string">'laptop'</span><span class="tok-punct">,</span><span class="tok-string">'charger'</span><span class="tok-punct">,</span><span class="tok-number">23.50</span><span class="tok-punct">,</span><span class="tok-punct">[</span><span class="tok-string">'gum'</span><span class="tok-punct">,</span><span class="tok-string">'mints'</span><span class="tok-punct">]</span><span class="tok-punct">]</span> <span class="tok-comment"># Make a List of stuff in my backpack</span>
<span class="tok-name">backpack</span> <span class="tok-operator">=</span> <span class="tok-name">backpack</span> <span class="tok-operator">+</span> <span class="tok-punct">[</span><span class="tok-string">'pen'</span><span class="tok-punct">]</span> <span class="tok-comment"># Add a pen to my backpack, note the pen is in a List</span>
<span class="tok-name">backpack</span> <span class="tok-operator">+=</span> <span class="tok-punct">[</span><span class="tok-string">'paper'</span><span class="tok-punct">,</span><span class="tok-string">'phone'</span><span class="tok-punct">]</span> <span class="tok-comment"># Add two more things</span>
<span class="tok-name">backpack</span> <span class="tok-operator">+=</span> <span class="tok-punct">(</span><span class="tok-string">'earbuds'</span><span class="tok-punct">,</span><span class="tok-string">'cashews'</span><span class="tok-punct">)</span> <span class="tok-comment"># Add two more things from a Tuple</span>
<span class="tok-name">backpack</span> <span class="tok-operator">+=</span> <span class="tok-punct">{</span><span class="tok-string">"breakfast"</span><span class="tok-punct">:</span><span class="tok-string">"eggs"</span><span class="tok-punct">,</span><span class="tok-string">"lunch"</span><span class="tok-punct">:</span><span class="tok-string">"noodles"</span><span class="tok-punct">}</span> <span class="tok-comment"># Add the lunch menu, NOTE: Only the keys are added (not the values)</span>
<span class="tok-name">backpack</span> <span class="tok-operator">+=</span> <span class="tok-punct">{</span><span class="tok-string">'glasses'</span><span class="tok-punct">,</span><span class="tok-string">'sweater'</span><span class="tok-punct">,</span><span class="tok-string">'watch'</span><span class="tok-punct">}</span> <span class="tok-comment"># Add three more things from a Set</span>
<span class="tok-comment"># backpack += 5 # Illegal: append operator only works with collections</span>
<span class="tok-comment"># Python Lists use the index operator to fetch items or Lists of items</span>
<span class="tok-name">backpack</span><span class="tok-punct">[</span><span class="tok-number">0</span><span class="tok-punct">]</span> <span class="tok-comment"># Get the first item in the List</span>
<span class="tok-name">backpack</span><span class="tok-punct">[</span><span class="tok-number">3</span><span class="tok-punct">]</span><span class="tok-punct">[</span><span class="tok-number">0</span><span class="tok-punct">]</span> <span class="tok-comment"># Get the first item of the fourth item in the List</span>
<span class="tok-name">backpack</span><span class="tok-punct">[</span><span class="tok-number">0</span><span class="tok-punct">:</span><span class="tok-number">3</span><span class="tok-punct">]</span> <span class="tok-comment"># Get a new List with the first three items at indexes 0, 1, and 2</span>
<span class="tok-name">backpack</span><span class="tok-punct">[</span><span class="tok-punct">:</span><span class="tok-number">3</span><span class="tok-punct">]</span> <span class="tok-comment"># Same as above, note the leading 0 is optional</span>
<span class="tok-name">backpack</span><span class="tok-punct">[</span><span class="tok-punct">:</span><span class="tok-punct">]</span> <span class="tok-comment"># Gets every item in the List</span>
<span class="tok-name">backpack</span><span class="tok-punct">[</span><span class="tok-number">4</span><span class="tok-punct">:</span><span class="tok-punct">]</span> <span class="tok-comment"># Get the fifth item and all items after it in the List</span>
<span class="tok-name">backpack</span><span class="tok-punct">[</span><span class="tok-operator">-</span><span class="tok-number">1</span><span class="tok-punct">]</span> <span class="tok-comment"># Get the last item in the List</span>
<span class="tok-name">backpack</span><span class="tok-punct">[</span><span class="tok-operator">-</span><span class="tok-number">2</span><span class="tok-punct">]</span> <span class="tok-comment"># Get the second to last item in the List</span>
<span class="tok-name">backpack</span><span class="tok-punct">[</span><span class="tok-operator">-</span><span class="tok-number">4</span><span class="tok-punct">:</span><span class="tok-operator">-</span><span class="tok-number">2</span><span class="tok-punct">]</span> <span class="tok-comment"># Get the fourth-to-last and third-to-last items in the List</span>
<span class="tok-name">backpack</span><span class="tok-punct">[</span><span class="tok-operator">-</span><span class="tok-number">3</span><span class="tok-punct">:</span><span class="tok-punct">]</span> <span class="tok-comment"># Get the third-to-last item and all subsequent items in the List</span>
<span class="tok-comment"># Python Lists use methods to add, remove and find items. backpack is our List.</span>
<span class="tok-name">backpack</span><span class="tok-punct">.</span><span class="tok-name">append</span><span class="tok-punct">(</span><span class="tok-number">5</span><span class="tok-punct">)</span> <span class="tok-comment"># Append will add anything to the backpack</span>
<span class="tok-name">how_many_pens</span> <span class="tok-operator">=</span> <span class="tok-name">backpack</span><span class="tok-punct">.</span><span class="tok-name">count</span><span class="tok-punct">(</span><span class="tok-string">'pen'</span><span class="tok-punct">)</span> <span class="tok-comment"># Count will count how many pens are in the backpack</span>
<span class="tok-name">where_is_my_paper</span> <span class="tok-operator">=</span> <span class="tok-name">backpack</span><span class="tok-punct">.</span><span class="tok-name">index</span><span class="tok-punct">(</span><span class="tok-string">'paper'</span><span class="tok-punct">)</span> <span class="tok-comment"># Index will find the first paper in the backpack</span>
<span class="tok-name">find_my_watch</span> <span class="tok-operator">=</span> <span class="tok-name">backpack</span><span class="tok-punct">.</span><span class="tok-name">index</span><span class="tok-punct">(</span><span class="tok-string">'watch'</span><span class="tok-punct">,</span><span class="tok-number">4</span><span class="tok-punct">)</span> <span class="tok-comment"># Index can find the watch but skip the first 4 items</span>
<span class="tok-name">find_my_earbuds</span> <span class="tok-operator">=</span> <span class="tok-name">backpack</span><span class="tok-punct">.</span><span class="tok-name">index</span><span class="tok-punct">(</span><span class="tok-string">'earbuds'</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-number">8</span><span class="tok-punct">)</span> <span class="tok-comment"># Index will find earbuds but skip the first 5 items and only check the next 3 items</span>
<span class="tok-name">backpack</span><span class="tok-punct">.</span><span class="tok-name">insert</span><span class="tok-punct">(</span><span class="tok-number">4</span><span class="tok-punct">,</span><span class="tok-string">'pen'</span><span class="tok-punct">)</span> <span class="tok-comment"># Insert will add another pen next to the current pen at index 4</span>
<span class="tok-name">backpack</span><span class="tok-punct">.</span><span class="tok-name">insert</span><span class="tok-punct">(</span><span class="tok-operator">-</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-string">'glasses'</span><span class="tok-punct">)</span> <span class="tok-comment"># Insert can add glasses next to the other glasses and the end of the List</span>
<span class="tok-name">five_bucks</span> <span class="tok-operator">=</span> <span class="tok-name">backpack</span><span class="tok-punct">.</span><span class="tok-name">pop</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Pop will take the 5 bucks back out of the backpack since they are the last item</span>
<span class="tok-name">laptop</span> <span class="tok-operator">=</span> <span class="tok-name">backpack</span><span class="tok-punct">.</span><span class="tok-name">pop</span><span class="tok-punct">(</span><span class="tok-number">0</span><span class="tok-punct">)</span> <span class="tok-comment"># Pop can also take the first (or any) item out of the backpack</span>
<span class="tok-name">backpack</span><span class="tok-punct">.</span><span class="tok-name">remove</span><span class="tok-punct">(</span><span class="tok-string">'sweater'</span><span class="tok-punct">)</span> <span class="tok-comment"># Remove will delete the sweater from the backpack</span>
<span class="tok-comment"># Python Lists can be sorted forwards or backwards</span>
<span class="tok-name">primes</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-number">11</span><span class="tok-punct">,</span><span class="tok-number">7</span><span class="tok-punct">,</span><span class="tok-number">13</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-number">3</span><span class="tok-punct">]</span> <span class="tok-comment"># Create an unsorted List of prime numbers</span>
<span class="tok-name">primes</span><span class="tok-punct">.</span><span class="tok-name">sort</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Sort the List in ascending order</span>
<span class="tok-name">primes</span><span class="tok-punct">.</span><span class="tok-name">sort</span><span class="tok-punct">(</span><span class="tok-name">reverse</span> <span class="tok-operator">=</span> <span class="tok-keyword">True</span><span class="tok-punct">)</span> <span class="tok-comment"># Sort the List in descending order</span>
<span class="tok-builtin">sorted</span><span class="tok-punct">(</span><span class="tok-name">primes</span><span class="tok-punct">)</span> <span class="tok-comment"># Use the built-in function sorted to sort the List instead</span>
<span class="tok-builtin">sorted</span><span class="tok-punct">(</span><span class="tok-name">primes</span><span class="tok-punct">,</span> <span class="tok-name">reverse</span> <span class="tok-operator">=</span> <span class="tok-keyword">True</span><span class="tok-punct">)</span> <span class="tok-comment"># Use the built-in function sorted to sort the List in reverse order</span>
<span class="tok-comment"># Python has built-in functions for List arithmetic</span>
<span class="tok-name">digits</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-number">8</span><span class="tok-punct">,</span><span class="tok-number">3</span><span class="tok-punct">,</span><span class="tok-number">7</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">4</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-number">6</span><span class="tok-punct">,</span><span class="tok-number">7</span><span class="tok-punct">]</span> <span class="tok-comment"># Make a List of some numbers</span>
<span class="tok-builtin">sum</span><span class="tok-punct">(</span><span class="tok-name">digits</span><span class="tok-punct">)</span> <span class="tok-comment"># Calculate the sum of the List of numbers</span>
<span class="tok-builtin">max</span><span class="tok-punct">(</span><span class="tok-name">digits</span><span class="tok-punct">)</span> <span class="tok-comment"># Find the largest (max) number in the List</span>
<span class="tok-builtin">min</span><span class="tok-punct">(</span><span class="tok-name">digits</span><span class="tok-punct">)</span> <span class="tok-comment"># Find the smallest (min) number is the List</span>
<span class="tok-comment"># Python has a statistics module for complex statistical analysis beyond simple arithmetic</span>
<span class="tok-keyword">from</span> <span class="tok-name">statistics</span> <span class="tok-keyword">import</span> <span class="tok-name">covariance</span><span class="tok-punct">,</span><span class="tok-name">fmean</span><span class="tok-punct">,</span><span class="tok-name">geometric_mean</span><span class="tok-punct">,</span><span class="tok-name">harmonic_mean</span><span class="tok-punct">,</span><span class="tok-name">kde</span> <span class="tok-comment"># Among others</span>
<span class="tok-comment"># Python allows you to combine Lists and Tuples together with concatenantion</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-string">'a'</span><span class="tok-punct">,</span><span class="tok-string">'b'</span><span class="tok-punct">,</span><span class="tok-string">'c'</span><span class="tok-punct">]</span> <span class="tok-operator">+</span> <span class="tok-punct">[</span><span class="tok-string">'d'</span><span class="tok-punct">,</span><span class="tok-string">'e'</span><span class="tok-punct">,</span><span class="tok-string">'f'</span><span class="tok-punct">]</span> <span class="tok-comment"># Concatenante two Lists</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-punct">(</span><span class="tok-string">'a'</span><span class="tok-punct">,</span><span class="tok-string">'b'</span><span class="tok-punct">,</span><span class="tok-string">'c'</span><span class="tok-punct">)</span> <span class="tok-operator">+</span> <span class="tok-punct">(</span><span class="tok-string">'d'</span><span class="tok-punct">,</span><span class="tok-string">'e'</span><span class="tok-punct">,</span><span class="tok-string">'f'</span><span class="tok-punct">)</span> <span class="tok-comment"># Concatenante two Tuples</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># List Comprehensions & Generators #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python has a unique way to create a List of items from another List called comprehensions</span>
<span class="tok-name">positive_integers</span> <span class="tok-operator">=</span> <span class="tok-builtin">list</span><span class="tok-punct">(</span><span class="tok-builtin">range</span><span class="tok-punct">(</span><span class="tok-number">100</span><span class="tok-punct">)</span><span class="tok-punct">)</span> <span class="tok-comment"># Make a List of positive integers from a range</span>
<span class="tok-name">odd_numbers</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-name">num</span> <span class="tok-keyword">for</span> <span class="tok-name">num</span> <span class="tok-keyword">in</span> <span class="tok-name">positive_integers</span> <span class="tok-keyword">if</span> <span class="tok-name">num</span> <span class="tok-operator">%</span> <span class="tok-number">2</span> <span class="tok-operator">==</span> <span class="tok-number">1</span><span class="tok-punct">]</span> <span class="tok-comment"># Use a List comprehension to extract the odd numbers</span>
<span class="tok-name">doubles</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-name">num</span> <span class="tok-operator">*</span> <span class="tok-number">2</span> <span class="tok-keyword">for</span> <span class="tok-name">num</span> <span class="tok-keyword">in</span> <span class="tok-name">positive_integers</span><span class="tok-punct">]</span> <span class="tok-comment"># Use a List comprehension to double each number</span>
<span class="tok-name">double_evens</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-name">num</span> <span class="tok-operator">*</span> <span class="tok-number">2</span> <span class="tok-keyword">for</span> <span class="tok-name">num</span> <span class="tok-keyword">in</span> <span class="tok-name">positive_integers</span> <span class="tok-keyword">if</span> <span class="tok-name">num</span> <span class="tok-operator">%</span> <span class="tok-number">2</span> <span class="tok-operator">==</span> <span class="tok-number">0</span><span class="tok-punct">]</span> <span class="tok-comment"># Find all the even numbers and multiple them by 2</span>
<span class="tok-comment"># Generators are useful for creating an iterator over a List especially in cases where the List is very large</span>
<span class="tok-name">double_evens_generator</span> <span class="tok-operator">=</span> <span class="tok-punct">(</span><span class="tok-name">num</span> <span class="tok-operator">*</span> <span class="tok-number">2</span> <span class="tok-keyword">for</span> <span class="tok-name">num</span> <span class="tok-keyword">in</span> <span class="tok-name">positive_integers</span> <span class="tok-keyword">if</span> <span class="tok-name">num</span> <span class="tok-operator">%</span> <span class="tok-number">2</span> <span class="tok-operator">==</span> <span class="tok-number">0</span><span class="tok-punct">)</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Dictionary Operations #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python dictionaries are hash tables with key: value pairs</span>
<span class="tok-name">locations</span> <span class="tok-operator">=</span> <span class="tok-punct">{</span><span class="tok-string">'orlando'</span><span class="tok-punct">:</span><span class="tok-string">'123 Brook Ln'</span><span class="tok-punct">,</span><span class="tok-string">'boston'</span><span class="tok-punct">:</span><span class="tok-string">'442 Green Pl'</span><span class="tok-punct">,</span><span class="tok-string">'houston'</span><span class="tok-punct">:</span><span class="tok-string">'12054 Industry Way'</span><span class="tok-punct">}</span> <span class="tok-comment"># Address book Dictionary</span>
<span class="tok-name">boston_addy</span> <span class="tok-operator">=</span> <span class="tok-name">locations</span><span class="tok-punct">[</span><span class="tok-string">'boston'</span><span class="tok-punct">]</span> <span class="tok-comment"># Get the address of the boston location with the index operator</span>
<span class="tok-name">boston_addy</span> <span class="tok-operator">=</span> <span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">get</span><span class="tok-punct">(</span><span class="tok-string">'boston'</span><span class="tok-punct">)</span> <span class="tok-comment"># Get the address with the get method</span>
<span class="tok-name">locations</span><span class="tok-punct">[</span><span class="tok-string">'orlando'</span><span class="tok-punct">]</span> <span class="tok-operator">=</span> <span class="tok-string">'133 Brook Ln'</span> <span class="tok-comment"># Update values with the assignment operator</span>
<span class="tok-name">locations</span><span class="tok-punct">[</span><span class="tok-string">'madison'</span><span class="tok-punct">]</span> <span class="tok-operator">=</span> <span class="tok-string">'890 State St'</span> <span class="tok-comment"># Add new values with the assignment operator</span>
<span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">update</span><span class="tok-punct">(</span> <span class="tok-comment"># Pass a Dictionary to update to add multiple values</span>
<span class="tok-punct">{</span><span class="tok-string">'flagstaff'</span><span class="tok-punct">:</span><span class="tok-string">'7370 Crane Way'</span><span class="tok-punct">,</span><span class="tok-string">'tempe'</span><span class="tok-punct">:</span><span class="tok-string">'9090 Locust St'</span><span class="tok-punct">}</span>
<span class="tok-punct">)</span>
<span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">update</span><span class="tok-punct">(</span> <span class="tok-comment"># We can pass a dictionary to update to change multiple values</span>
<span class="tok-punct">{</span><span class="tok-string">'boston'</span><span class="tok-punct">:</span><span class="tok-string">'443 Green Pl'</span><span class="tok-punct">,</span><span class="tok-string">'houston'</span><span class="tok-punct">:</span><span class="tok-string">'12054 Industry Blvd'</span><span class="tok-punct">}</span>
<span class="tok-punct">)</span>
<span class="tok-name">boston</span> <span class="tok-operator">=</span> <span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">pop</span><span class="tok-punct">(</span><span class="tok-string">'boston'</span><span class="tok-punct">)</span> <span class="tok-comment"># We can remove a key value pair with the pop method fetching the value</span>
<span class="tok-comment"># Python will throw a KeyError if we attempt to access a non-existent pair</span>
<span class="tok-keyword">if</span> <span class="tok-string">'sarasota'</span> <span class="tok-keyword">in</span> <span class="tok-name">locations</span><span class="tok-punct">:</span> <span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">locations</span><span class="tok-punct">[</span><span class="tok-string">'sarasota'</span><span class="tok-punct">]</span><span class="tok-punct">)</span> <span class="tok-comment"># We can test for a key with the in keyword</span>
<span class="tok-name">sarasota</span> <span class="tok-operator">=</span> <span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">get</span><span class="tok-punct">(</span><span class="tok-string">'sarasota'</span><span class="tok-punct">)</span> <span class="tok-comment"># We can also test using the get method (returns None)</span>
<span class="tok-name">sarasota</span> <span class="tok-operator">=</span> <span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">get</span><span class="tok-punct">(</span><span class="tok-string">'sarasota'</span><span class="tok-punct">,</span><span class="tok-string">'100 Nowhere Dr'</span><span class="tok-punct">)</span> <span class="tok-comment"># We can also return a default value instead of None</span>
<span class="tok-name">boston</span> <span class="tok-operator">=</span> <span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">pop</span><span class="tok-punct">(</span><span class="tok-string">'boston'</span><span class="tok-punct">,</span><span class="tok-string">'100 Nowhere Dr'</span><span class="tok-punct">)</span> <span class="tok-comment"># Pop also supports default values</span>
<span class="tok-builtin">list</span><span class="tok-punct">(</span><span class="tok-name">locations</span><span class="tok-punct">)</span> <span class="tok-comment"># Gets a List of keys in the Dictionary</span>
<span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">keys</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Gets an immutable set of keys in the Dictionary</span>
<span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">values</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Gets an values iterator</span>
<span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">items</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Gets a (key,value) Tuple iterator</span>
<span class="tok-keyword">for</span> <span class="tok-name">kvp</span> <span class="tok-keyword">in</span> <span class="tok-name">locations</span><span class="tok-punct">:</span> <span class="tok-comment"># Iterating the Dictionary returns the key strings</span>
<span class="tok-name">value</span> <span class="tok-operator">=</span> <span class="tok-name">locations</span><span class="tok-punct">[</span><span class="tok-name">kvp</span><span class="tok-punct">]</span>
<span class="tok-keyword">for</span> <span class="tok-name">city</span><span class="tok-punct">,</span><span class="tok-name">addr</span> <span class="tok-keyword">in</span> <span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">items</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-comment"># Iterating the items returns key,value Tuples</span>
<span class="tok-name">text</span> <span class="tok-operator">=</span> f'<span class="tok-punct">{</span><span class="tok-name">city</span><span class="tok-punct">}</span>: <span class="tok-punct">{</span><span class="tok-name">addr</span><span class="tok-punct">}</span>'
<span class="tok-keyword">for</span> <span class="tok-name">city_addr</span> <span class="tok-keyword">in</span> <span class="tok-name">locations</span><span class="tok-punct">.</span><span class="tok-name">items</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-comment"># If you do not declare the Tuple parts, you can access</span>
<span class="tok-name">key</span> <span class="tok-operator">=</span> <span class="tok-name">city_addr</span><span class="tok-punct">[</span><span class="tok-number">0</span><span class="tok-punct">]</span> <span class="tok-comment"># each Tuple point by index number</span>
<span class="tok-name">value</span> <span class="tok-operator">=</span> <span class="tok-name">city_addr</span><span class="tok-punct">[</span><span class="tok-number">1</span><span class="tok-punct">]</span>
<span class="tok-comment"># Dictionaries, like Lists, have comprehensions which can be used to create Dictionaries from Lists</span>
<span class="tok-name">students</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-string">'Alice'</span><span class="tok-punct">,</span><span class="tok-string">'Bob'</span><span class="tok-punct">,</span><span class="tok-string">'Charlie'</span><span class="tok-punct">,</span><span class="tok-string">'David'</span><span class="tok-punct">,</span><span class="tok-string">'Ethan'</span><span class="tok-punct">]</span>
<span class="tok-name">test_scores</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-number">99</span><span class="tok-punct">,</span><span class="tok-number">98</span><span class="tok-punct">,</span><span class="tok-number">99</span><span class="tok-punct">,</span><span class="tok-number">91</span><span class="tok-punct">,</span><span class="tok-number">92</span><span class="tok-punct">]</span>
<span class="tok-name">zipped</span> <span class="tok-operator">=</span> <span class="tok-builtin">zip</span><span class="tok-punct">(</span><span class="tok-name">students</span><span class="tok-punct">,</span><span class="tok-name">test_scores</span><span class="tok-punct">)</span> <span class="tok-comment"># Zip is a class which can merge Lists into Tuples</span>
<span class="tok-name">student_scores</span> <span class="tok-operator">=</span> <span class="tok-punct">{</span><span class="tok-name">key</span><span class="tok-punct">:</span><span class="tok-name">value</span> <span class="tok-keyword">for</span> <span class="tok-name">key</span><span class="tok-punct">,</span> <span class="tok-name">value</span> <span class="tok-keyword">in</span> <span class="tok-name">zipped</span><span class="tok-punct">}</span> <span class="tok-comment"># Using a Dictionary comprehension we can merge students with test_scores</span>
<span class="tok-comment"># Dictionary comprehensions require Tuples rather than items since Dictionary entries are key-value pairs</span>
<span class="tok-name">score_list</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-punct">[</span><span class="tok-string">'Alice'</span><span class="tok-punct">,</span><span class="tok-number">99</span><span class="tok-punct">]</span><span class="tok-punct">,</span><span class="tok-punct">[</span><span class="tok-string">'Bob'</span><span class="tok-punct">,</span><span class="tok-number">98</span><span class="tok-punct">]</span><span class="tok-punct">,</span><span class="tok-punct">[</span><span class="tok-string">'Charlie'</span><span class="tok-punct">,</span><span class="tok-number">99</span><span class="tok-punct">]</span><span class="tok-punct">]</span> <span class="tok-comment"># Here we have a two-dimensional array</span>
<span class="tok-name">student_scores</span> <span class="tok-operator">=</span> <span class="tok-punct">{</span><span class="tok-name">n</span><span class="tok-punct">[</span><span class="tok-number">0</span><span class="tok-punct">]</span><span class="tok-punct">:</span><span class="tok-name">n</span><span class="tok-punct">[</span><span class="tok-number">1</span><span class="tok-punct">]</span> <span class="tok-keyword">for</span> <span class="tok-name">n</span> <span class="tok-keyword">in</span> <span class="tok-name">score_list</span><span class="tok-punct">}</span> <span class="tok-comment"># Merge the two-dimensional array into a Dictionary</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Dates & Times #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python date and time operations are implemented in the datetime module</span>
<span class="tok-keyword">from</span> <span class="tok-name">datetime</span> <span class="tok-keyword">import</span> <span class="tok-name">datetime</span> <span class="tok-comment"># Datetime is a class in the datetime module</span>
<span class="tok-name">back_then</span> <span class="tok-operator">=</span> <span class="tok-name">datetime</span><span class="tok-punct">(</span><span class="tok-number">2025</span><span class="tok-punct">,</span><span class="tok-number">7</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-number">9</span><span class="tok-punct">,</span><span class="tok-number">38</span><span class="tok-punct">,</span><span class="tok-number">25</span><span class="tok-punct">)</span> <span class="tok-comment"># Construct a datetime with its constituent parts</span>
<span class="tok-name">right_now</span> <span class="tok-operator">=</span> <span class="tok-name">datetime</span><span class="tok-punct">.</span><span class="tok-name">now</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Get the current time and date</span>
<span class="tok-name">right_now</span> <span class="tok-operator">-</span> <span class="tok-name">back_then</span> <span class="tok-comment"># Get the difference between two datetimes</span>
<span class="tok-name">a_while_ago</span> <span class="tok-operator">=</span> \
<span class="tok-name">datetime</span><span class="tok-punct">.</span><span class="tok-name">strptime</span><span class="tok-punct">(</span><span class="tok-string">'Mar 10, 1993'</span><span class="tok-punct">,</span><span class="tok-string">'%b %d, %Y'</span><span class="tok-punct">)</span> <span class="tok-comment"># Parse a String into a datetime</span>
<span class="tok-name">welcome_to_now</span> <span class="tok-operator">=</span> <span class="tok-name">right_now</span><span class="tok-punct">.</span><span class="tok-name">strftime</span><span class="tok-punct">(</span><span class="tok-string">'%d/%m/%Y'</span><span class="tok-punct">)</span> <span class="tok-comment"># Format the current time and date into a String</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># 3. Control Flow #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># If Statements #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python conditional control flow uses the if, elif, and else keywords where indentation tells the Python</span>
<span class="tok-comment"># interpreter which instructions to run if the condition is met</span>
<span class="tok-name">my_name</span> <span class="tok-operator">=</span> <span class="tok-string">'Bob'</span>
<span class="tok-keyword">if</span> <span class="tok-name">my_name</span> <span class="tok-operator">==</span> <span class="tok-string">'Christian'</span><span class="tok-punct">:</span> <span class="tok-comment"># If this is True</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'My name is Christian'</span><span class="tok-punct">)</span> <span class="tok-comment"># Run this line</span>
<span class="tok-keyword">if</span> <span class="tok-name">my_name</span> <span class="tok-operator">==</span> <span class="tok-string">'Christian'</span><span class="tok-punct">:</span> <span class="tok-comment"># If this is True</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'My name is Christian'</span><span class="tok-punct">)</span> <span class="tok-comment"># Run this line</span>
<span class="tok-keyword">else</span><span class="tok-punct">:</span> <span class="tok-comment"># Otherwise...</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'My name is not Christian'</span><span class="tok-punct">)</span> <span class="tok-comment"># Run this line instead</span>
<span class="tok-keyword">if</span> <span class="tok-name">my_name</span> <span class="tok-operator">==</span> <span class="tok-string">'Christian'</span><span class="tok-punct">:</span> <span class="tok-comment"># If this is True</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'My name is Christian'</span><span class="tok-punct">)</span> <span class="tok-comment"># Run this</span>
<span class="tok-keyword">elif</span> <span class="tok-name">my_name</span> <span class="tok-operator">==</span> <span class="tok-string">'Bob'</span><span class="tok-punct">:</span> <span class="tok-comment"># Or if this is True, and the previous expression was False</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'My name is Bob'</span><span class="tok-punct">)</span> <span class="tok-comment"># Run this line</span>
<span class="tok-keyword">else</span><span class="tok-punct">:</span> <span class="tok-comment"># Otherwise...</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'Who am I?'</span><span class="tok-punct">)</span> <span class="tok-comment"># Run this line instead</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Loops #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python loop control includes for loops and while loops</span>
<span class="tok-keyword">for</span> <span class="tok-name">item</span> <span class="tok-keyword">in</span> <span class="tok-name">backpack</span><span class="tok-punct">:</span> <span class="tok-comment"># Iterate over all items in a collection</span>
<span class="tok-name">my_item</span> <span class="tok-operator">=</span> <span class="tok-name">item</span>
<span class="tok-name">x</span> <span class="tok-operator">=</span> <span class="tok-number">0</span>
<span class="tok-keyword">while</span> <span class="tok-name">x</span> <span class="tok-operator"><</span> <span class="tok-builtin">len</span><span class="tok-punct">(</span><span class="tok-name">backpack</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-comment"># Loop while a condition is True</span>
<span class="tok-name">x</span> <span class="tok-operator">+=</span> <span class="tok-number">1</span>
<span class="tok-comment"># Python loops support break and continue statements which will stop the loop or skip steps, respectively</span>
<span class="tok-keyword">for</span> <span class="tok-name">item</span> <span class="tok-keyword">in</span> <span class="tok-name">backpack</span><span class="tok-punct">:</span> <span class="tok-comment"># This will loop through the backpack until we find paper</span>
<span class="tok-keyword">if</span> <span class="tok-name">item</span> <span class="tok-operator">==</span> <span class="tok-string">'paper'</span><span class="tok-punct">:</span>
<span class="tok-keyword">break</span>
<span class="tok-keyword">else</span><span class="tok-punct">:</span>
<span class="tok-name">not_paper</span> <span class="tok-operator">=</span> <span class="tok-name">item</span>
<span class="tok-keyword">for</span> <span class="tok-name">item</span> <span class="tok-keyword">in</span> <span class="tok-name">backpack</span><span class="tok-punct">:</span> <span class="tok-comment"># This will loop through the entire backpack but will not print any paper</span>
<span class="tok-keyword">if</span> <span class="tok-name">item</span> <span class="tok-operator">==</span> <span class="tok-string">'paper'</span><span class="tok-punct">:</span>
<span class="tok-keyword">continue</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">item</span><span class="tok-punct">)</span>
<span class="tok-comment"># The pass keyword is used for doing a no-op (No Operation)</span>
<span class="tok-keyword">for</span> <span class="tok-name">item</span> <span class="tok-keyword">in</span> <span class="tok-name">backpack</span><span class="tok-punct">:</span> <span class="tok-comment"># This will loop through the entire backpack and do nothing with each item</span>
<span class="tok-keyword">pass</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Branching / Switching #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python uses the match statement to create a switch case branch</span>
<span class="tok-name">letter</span> <span class="tok-operator">=</span> <span class="tok-string">'q'</span> <span class="tok-comment"># The letter is q</span>
<span class="tok-name">match</span> <span class="tok-name">letter</span><span class="tok-punct">:</span> <span class="tok-comment"># Create a 'ladder' of matches for what the letter might be</span>
<span class="tok-name">case</span> <span class="tok-string">'a'</span><span class="tok-punct">:</span> <span class="tok-comment"># If letter is a ...</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'a is for aardvark'</span><span class="tok-punct">)</span>
<span class="tok-name">case</span> <span class="tok-string">'b'</span><span class="tok-punct">:</span> <span class="tok-comment"># If letter is b ...</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'b is for boysenberry'</span><span class="tok-punct">)</span>
<span class="tok-name">case</span> <span class="tok-name">default</span><span class="tok-punct">:</span> <span class="tok-comment"># Use default to do something if there is no match</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">letter</span><span class="tok-punct">)</span>
<span class="tok-comment"># The match statement was added recently in Python 3.10, the above code will fail if you run this on older Python runtimes</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># 4. Functions #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># User-Defined Functions #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python allows you to define your own functions which are blocks of reusable code</span>
<span class="tok-keyword">def</span> <span class="tok-name">my_function</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">:</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'Hello, world!'</span><span class="tok-punct">)</span>
<span class="tok-comment"># Python user-defined functions can return zero, one or more values</span>
<span class="tok-keyword">def</span> <span class="tok-name">returns_nothing</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'Hello, world!'</span><span class="tok-punct">)</span> <span class="tok-comment"># Returns nothing</span>
<span class="tok-keyword">def</span> <span class="tok-name">returns_something</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-keyword">return</span> <span class="tok-string">'Hello, world!'</span> <span class="tok-comment"># Returns a String</span>
<span class="tok-keyword">def</span> <span class="tok-name">returns_three_values</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-keyword">return</span> <span class="tok-string">'Hello'</span><span class="tok-punct">,</span> <span class="tok-string">'world'</span><span class="tok-punct">,</span> <span class="tok-string">'!'</span> <span class="tok-comment"># Returns three separate values</span>
<span class="tok-comment"># Return values are assigned to one or more variables using the assignment (=) operator</span>
<span class="tok-name">returns_nothing</span><span class="tok-punct">(</span><span class="tok-punct">)</span>
<span class="tok-name">hello_world</span> <span class="tok-operator">=</span> <span class="tok-name">returns_something</span><span class="tok-punct">(</span><span class="tok-punct">)</span>
<span class="tok-name">hello</span><span class="tok-punct">,</span> <span class="tok-name">world</span><span class="tok-punct">,</span> <span class="tok-name">exclaim</span> <span class="tok-operator">=</span> <span class="tok-name">returns_three_values</span><span class="tok-punct">(</span><span class="tok-punct">)</span>
<span class="tok-comment"># Function arguments and their parameters can be passed in positional or keyword format</span>
<span class="tok-keyword">def</span> <span class="tok-name">calc_product</span><span class="tok-punct">(</span><span class="tok-name">a</span><span class="tok-punct">,</span> <span class="tok-name">b</span><span class="tok-punct">,</span> <span class="tok-name">c</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-keyword">return</span> <span class="tok-name">a</span> <span class="tok-operator">*</span> <span class="tok-name">b</span> <span class="tok-operator">*</span> <span class="tok-name">c</span>
<span class="tok-name">calc_product</span><span class="tok-punct">(</span><span class="tok-number">1</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">3</span><span class="tok-punct">)</span> <span class="tok-comment"># These parameters are passed by position</span>
<span class="tok-name">calc_product</span><span class="tok-punct">(</span><span class="tok-name">b</span> <span class="tok-operator">=</span> <span class="tok-number">2</span><span class="tok-punct">,</span> <span class="tok-name">c</span> <span class="tok-operator">=</span> <span class="tok-number">3</span><span class="tok-punct">,</span> <span class="tok-name">a</span> <span class="tok-operator">=</span> <span class="tok-number">1</span><span class="tok-punct">)</span> <span class="tok-comment"># These parameters are passed by keyword</span>
<span class="tok-name">calc_product</span><span class="tok-punct">(</span><span class="tok-number">4</span><span class="tok-punct">,</span> <span class="tok-name">c</span> <span class="tok-operator">=</span> <span class="tok-number">12</span><span class="tok-punct">,</span> <span class="tok-name">b</span> <span class="tok-operator">=</span> <span class="tok-number">7</span><span class="tok-punct">)</span> <span class="tok-comment"># These parameters are mixed between position and keyword</span>
<span class="tok-comment"># This makes Python functions more versatile than many other languages</span>
<span class="tok-comment"># You can specify only the parameters relevant to you</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'No line break'</span><span class="tok-punct">,</span> <span class="tok-name">end</span> <span class="tok-operator">=</span> <span class="tok-string">''</span><span class="tok-punct">)</span> <span class="tok-comment"># For example, you can print text with no line break</span>
<span class="tok-comment"># Function definitions can have default argument values</span>
<span class="tok-keyword">def</span> <span class="tok-name">say_my_name</span><span class="tok-punct">(</span><span class="tok-name">name</span> <span class="tok-operator">=</span> <span class="tok-string">'Christian'</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">name</span><span class="tok-punct">)</span> <span class="tok-comment"># This function's name argument is defaulted</span>
<span class="tok-name">say_my_name</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Calling it this way prints the default value</span>
<span class="tok-name">say_my_name</span><span class="tok-punct">(</span><span class="tok-string">'Alice'</span><span class="tok-punct">)</span> <span class="tok-comment"># Calling it this way prints Alice</span>
<span class="tok-name">say_my_name</span><span class="tok-punct">(</span><span class="tok-name">name</span> <span class="tok-operator">=</span> <span class="tok-string">'Bob'</span><span class="tok-punct">)</span> <span class="tok-comment"># Calling it this way prints Bob</span>
<span class="tok-comment"># Functions also support arbitrary positional arguments</span>
<span class="tok-keyword">def</span> <span class="tok-name">add_numbers</span><span class="tok-punct">(</span><span class="tok-operator">*</span><span class="tok-name">nums</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-comment"># Using *nums means you can specify an unlimited number of nums</span>
<span class="tok-name">result</span> <span class="tok-operator">=</span> <span class="tok-number">0</span> <span class="tok-comment"># as the first positional argument which will be passed as a List</span>
<span class="tok-keyword">for</span> <span class="tok-name">i</span> <span class="tok-keyword">in</span> <span class="tok-name">nums</span><span class="tok-punct">:</span> <span class="tok-comment"># Here we iterate the nums List</span>
<span class="tok-name">result</span> <span class="tok-operator">+=</span> <span class="tok-name">i</span>
<span class="tok-keyword">return</span> <span class="tok-name">result</span>
<span class="tok-name">add_numbers</span><span class="tok-punct">(</span><span class="tok-number">3</span><span class="tok-punct">,</span><span class="tok-number">7</span><span class="tok-punct">,</span><span class="tok-number">4</span><span class="tok-punct">,</span><span class="tok-number">2</span><span class="tok-punct">,</span><span class="tok-number">8</span><span class="tok-punct">,</span><span class="tok-number">3</span><span class="tok-punct">,</span><span class="tok-number">4</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-number">6</span><span class="tok-punct">)</span> <span class="tok-comment"># We call the function with a bunch of numbers</span>
<span class="tok-comment"># Functions also support abritrary keyword arguments</span>
<span class="tok-keyword">def</span> <span class="tok-name">print_brochure</span><span class="tok-punct">(</span><span class="tok-operator">**</span><span class="tok-name">tags</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-comment"># The double asterisk (**) token means we accept arbitrary named parameters</span>
<span class="tok-keyword">for</span> <span class="tok-name">key</span><span class="tok-punct">,</span> <span class="tok-name">value</span> <span class="tok-keyword">in</span> <span class="tok-name">tags</span><span class="tok-punct">.</span><span class="tok-name">items</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-comment"># The tags argument will come in as a Dictionary</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span>f"<span class="tok-punct">{</span><span class="tok-name">key</span><span class="tok-punct">}</span> = <span class="tok-punct">{</span><span class="tok-name">value</span><span class="tok-punct">}</span>"<span class="tok-punct">)</span>
<span class="tok-name">print_brochure</span><span class="tok-punct">(</span> <span class="tok-name">breakfast</span> <span class="tok-operator">=</span> <span class="tok-string">'eggs'</span><span class="tok-punct">,</span> <span class="tok-name">lunch</span> <span class="tok-operator">=</span> <span class="tok-string">'salad'</span><span class="tok-punct">,</span> <span class="tok-name">dinner</span> <span class="tok-operator">=</span> <span class="tok-string">'pasta'</span><span class="tok-punct">)</span> <span class="tok-comment"># This is what they look like</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Anonymous Functions (Lambda) #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python supports anonymous functions called lambda functions</span>
<span class="tok-name">positive_integers</span> <span class="tok-operator">=</span> <span class="tok-builtin">list</span><span class="tok-punct">(</span><span class="tok-builtin">range</span><span class="tok-punct">(</span><span class="tok-number">100</span><span class="tok-punct">)</span><span class="tok-punct">)</span>
<span class="tok-name">odd_numbers</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-name">num</span> <span class="tok-keyword">for</span> <span class="tok-name">num</span> <span class="tok-keyword">in</span> <span class="tok-name">positive_integers</span> <span class="tok-keyword">if</span> <span class="tok-name">num</span> <span class="tok-operator">%</span> <span class="tok-number">2</span> <span class="tok-operator">==</span> <span class="tok-number">1</span><span class="tok-punct">]</span>
<span class="tok-name">odd_numbers</span> <span class="tok-operator">=</span> <span class="tok-builtin">list</span><span class="tok-punct">(</span><span class="tok-builtin">filter</span><span class="tok-punct">(</span><span class="tok-keyword">lambda</span> <span class="tok-name">x</span><span class="tok-punct">:</span> <span class="tok-name">x</span> <span class="tok-operator">%</span> <span class="tok-number">2</span> <span class="tok-operator">==</span> <span class="tok-number">1</span><span class="tok-punct">,</span> <span class="tok-name">positive_integers</span><span class="tok-punct">)</span><span class="tok-punct">)</span> <span class="tok-comment"># Here we use a lambda function to find all the</span>
<span class="tok-comment"># odd numbers in a list of numbers using the filter</span>
<span class="tok-comment"># function which accepts a function as the first parameter</span>
<span class="tok-comment"># Lambda functions can have multiple arguments that can map into the caller parameters</span>
<span class="tok-comment"># In the example below we are passing two iterables to the map function thus our</span>
<span class="tok-comment"># Lambda function will be defined with two arguments, in order, one for the first</span>
<span class="tok-comment"># And one for the second iterable</span>
<span class="tok-name">products</span> <span class="tok-operator">=</span> <span class="tok-builtin">list</span><span class="tok-punct">(</span><span class="tok-builtin">map</span><span class="tok-punct">(</span><span class="tok-keyword">lambda</span> <span class="tok-name">x</span><span class="tok-punct">,</span> <span class="tok-name">y</span><span class="tok-punct">:</span> <span class="tok-name">x</span> <span class="tok-operator">*</span> <span class="tok-name">y</span><span class="tok-punct">,</span> <span class="tok-name">odd_numbers</span><span class="tok-punct">,</span> <span class="tok-name">odd_numbers</span><span class="tok-punct">)</span><span class="tok-punct">)</span>
<span class="tok-comment"># Here is another examples with two different lists</span>
<span class="tok-name">menu_items</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-string">'Eggs'</span><span class="tok-punct">,</span><span class="tok-string">'Sausage'</span><span class="tok-punct">,</span><span class="tok-string">'Toast'</span><span class="tok-punct">,</span><span class="tok-string">'Coffee'</span><span class="tok-punct">]</span>
<span class="tok-name">menu_prices</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-string">'2.99'</span><span class="tok-punct">,</span><span class="tok-string">'3.99'</span><span class="tok-punct">,</span><span class="tok-string">'1.99'</span><span class="tok-punct">,</span><span class="tok-string">'2.00'</span><span class="tok-punct">]</span>
<span class="tok-name">menu</span> <span class="tok-operator">=</span> <span class="tok-builtin">list</span><span class="tok-punct">(</span><span class="tok-builtin">map</span><span class="tok-punct">(</span><span class="tok-keyword">lambda</span> <span class="tok-name">x</span><span class="tok-punct">,</span> <span class="tok-name">y</span><span class="tok-punct">:</span> f'<span class="tok-punct">{</span><span class="tok-name">x</span><span class="tok-punct">}</span>: $<span class="tok-punct">{</span><span class="tok-name">y</span><span class="tok-punct">}</span>'<span class="tok-punct">,</span> <span class="tok-name">menu_items</span><span class="tok-punct">,</span> <span class="tok-name">menu_prices</span><span class="tok-punct">)</span><span class="tok-punct">)</span> <span class="tok-comment"># Makes a List of menu items by name and price</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">menu</span><span class="tok-punct">)</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># 5. I/O #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># File System #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Let's setup some data we can use for these examples</span>
<span class="tok-name">data_dump_text</span> <span class="tok-operator">=</span> <span class="tok-string">'Task,Estimate,Notes\nDo laundry,3,Three loads of lights darks and colds\nEat breakfast,1,Eggs and toast with coffee\nMake the bed,0.25,Change the sheets and fluff the pillows'</span>
<span class="tok-name">data_dump_task</span> <span class="tok-operator">=</span> <span class="tok-string">'Drink water,8,Stay hydrated'</span>
<span class="tok-comment"># Python uses the open function to access local files on the file system</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'python_primer.py'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">primer_file</span><span class="tok-punct">:</span>
<span class="tok-name">python_primer</span> <span class="tok-operator">=</span> <span class="tok-name">primer_file</span><span class="tok-punct">.</span><span class="tok-name">read</span><span class="tok-punct">(</span><span class="tok-punct">)</span>
<span class="tok-comment"># Python has a readlines method for reading text files line by line</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'python_primer.py'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">primer_file</span><span class="tok-punct">:</span> <span class="tok-comment"># By default, files are opened in read mode</span>
<span class="tok-name">line_count</span> <span class="tok-operator">=</span> <span class="tok-number">0</span>
<span class="tok-keyword">for</span> <span class="tok-name">line</span> <span class="tok-keyword">in</span> <span class="tok-name">primer_file</span><span class="tok-punct">.</span><span class="tok-name">readlines</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">:</span>
<span class="tok-name">new_line</span> <span class="tok-operator">=</span> f': <span class="tok-punct">{</span><span class="tok-name">line</span><span class="tok-punct">}</span>'
<span class="tok-name">line_count</span> <span class="tok-operator">+=</span> <span class="tok-number">1</span>
<span class="tok-comment"># You'll notice that the variables declared inside the with block persist outside</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span>f'python_primer.py contains <span class="tok-punct">{</span><span class="tok-name">line_count</span><span class="tok-punct">}</span> lines'<span class="tok-punct">)</span>
<span class="tok-comment"># Python supports writing to files with the same function</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'data_dump.csv'</span><span class="tok-punct">,</span> <span class="tok-string">'w'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">primer_copy</span><span class="tok-punct">:</span> <span class="tok-comment"># The 'w' argument indicates write mode</span>
<span class="tok-name">primer_copy</span><span class="tok-punct">.</span><span class="tok-name">write</span><span class="tok-punct">(</span><span class="tok-name">data_dump_text</span><span class="tok-punct">)</span>
<span class="tok-comment"># Python uses the mode parameter to determine how the file is opened:</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'data_dump.csv'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">data_dump</span><span class="tok-punct">:</span> <span class="tok-comment"># No argument defaults to read</span>
<span class="tok-name">data</span> <span class="tok-operator">=</span> <span class="tok-name">data_dump</span><span class="tok-punct">.</span><span class="tok-name">read</span><span class="tok-punct">(</span><span class="tok-punct">)</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'data_dump.csv'</span><span class="tok-punct">,</span><span class="tok-string">'r'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">data_dump</span><span class="tok-punct">:</span> <span class="tok-comment"># Passing r is for read</span>
<span class="tok-name">data</span> <span class="tok-operator">=</span> <span class="tok-name">data_dump</span><span class="tok-punct">.</span><span class="tok-name">read</span><span class="tok-punct">(</span><span class="tok-punct">)</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'data_dump.csv'</span><span class="tok-punct">,</span><span class="tok-string">'w'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">data_dump</span><span class="tok-punct">:</span> <span class="tok-comment"># Passing w is for write (overwrite)</span>
<span class="tok-name">data_dump</span><span class="tok-punct">.</span><span class="tok-name">write</span><span class="tok-punct">(</span><span class="tok-name">data_dump_text</span><span class="tok-punct">)</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'data_dump.csv'</span><span class="tok-punct">,</span><span class="tok-string">'a'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">data_dump</span><span class="tok-punct">:</span> <span class="tok-comment"># Passing a is for append</span>
<span class="tok-name">data_dump</span><span class="tok-punct">.</span><span class="tok-name">write</span><span class="tok-punct">(</span>f'\n<span class="tok-punct">{</span><span class="tok-name">data_dump_task</span><span class="tok-punct">}</span>'<span class="tok-punct">)</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># File System: CSV Format #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python has a clever way to read CSV data from the file system</span>
<span class="tok-keyword">import</span> <span class="tok-name">csv</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'data_dump.csv'</span><span class="tok-punct">,</span><span class="tok-name">newline</span><span class="tok-operator">=</span><span class="tok-string">''</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">data_dump</span><span class="tok-punct">:</span>
<span class="tok-name">reader</span> <span class="tok-operator">=</span> <span class="tok-name">csv</span><span class="tok-punct">.</span><span class="tok-name">DictReader</span><span class="tok-punct">(</span><span class="tok-name">data_dump</span><span class="tok-punct">)</span> <span class="tok-comment"># The DictReader parses the header and treats each line</span>
<span class="tok-keyword">for</span> <span class="tok-builtin">dict</span> <span class="tok-keyword">in</span> <span class="tok-name">reader</span><span class="tok-punct">:</span> <span class="tok-comment"># of data as a Dictionary for access via named property</span>
<span class="tok-name">task</span> <span class="tok-operator">=</span> <span class="tok-builtin">dict</span><span class="tok-punct">[</span><span class="tok-string">'Task'</span><span class="tok-punct">]</span>
<span class="tok-name">estimate</span> <span class="tok-operator">=</span> <span class="tok-builtin">dict</span><span class="tok-punct">[</span><span class="tok-string">'Estimate'</span><span class="tok-punct">]</span>
<span class="tok-name">notes</span> <span class="tok-operator">=</span> <span class="tok-builtin">dict</span><span class="tok-punct">[</span><span class="tok-string">'Notes'</span><span class="tok-punct">]</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span>f'<span class="tok-punct">{</span><span class="tok-name">task</span><span class="tok-punct">}</span>: (<span class="tok-punct">{</span><span class="tok-name">estimate</span><span class="tok-punct">}</span> hours) - <span class="tok-punct">{</span><span class="tok-name">notes</span><span class="tok-punct">}</span>'<span class="tok-punct">)</span>
<span class="tok-comment"># In the example above the DictReader function from the CSV module returns an iterable</span>
<span class="tok-comment"># Dictionary reader for the CSV file which converts each line of the CSV file into a Dictionary</span>
<span class="tok-comment"># object which we can then use to access each value by name from the current line in the file</span>
<span class="tok-comment"># Let's make a PSV file (pipe-separated values) for our next example</span>
<span class="tok-name">psv_data</span> <span class="tok-operator">=</span> <span class="tok-string">'Ingredient|Amount|Prep\nBeef|2 lbs|Thaw, cook then set aside\nPotatoes|12 large|Skin, boil, mash then let cool\nCream|2 cups|Warm then stir into beef and potatoes'</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'hotdish_recipe.psv'</span><span class="tok-punct">,</span><span class="tok-string">'w'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">psv</span><span class="tok-punct">:</span> <span class="tok-name">psv</span><span class="tok-punct">.</span><span class="tok-name">write</span><span class="tok-punct">(</span><span class="tok-name">psv_data</span><span class="tok-punct">)</span>
<span class="tok-comment"># What's nice about csv.DictReader is it will accept arbitrary delimiters so we do not have</span>
<span class="tok-comment"># to use commas to separate values in files, we can use less common text characters such as</span>
<span class="tok-comment"># pipes (|) or semicolons (;)</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'hotdish_recipe.psv'</span><span class="tok-punct">,</span><span class="tok-name">newline</span><span class="tok-operator">=</span><span class="tok-string">''</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">recipe</span><span class="tok-punct">:</span>
<span class="tok-name">reader</span> <span class="tok-operator">=</span> <span class="tok-name">csv</span><span class="tok-punct">.</span><span class="tok-name">DictReader</span><span class="tok-punct">(</span><span class="tok-name">recipe</span><span class="tok-punct">,</span><span class="tok-name">delimiter</span><span class="tok-operator">=</span><span class="tok-string">'|'</span><span class="tok-punct">)</span> <span class="tok-comment"># The delimiter keyword parameter lets us use the pipe character</span>
<span class="tok-keyword">for</span> <span class="tok-builtin">dict</span> <span class="tok-keyword">in</span> <span class="tok-name">reader</span><span class="tok-punct">:</span>
<span class="tok-name">ingredient</span> <span class="tok-operator">=</span> <span class="tok-builtin">dict</span><span class="tok-punct">[</span><span class="tok-string">'Ingredient'</span><span class="tok-punct">]</span>
<span class="tok-name">amount</span> <span class="tok-operator">=</span> <span class="tok-builtin">dict</span><span class="tok-punct">[</span><span class="tok-string">'Amount'</span><span class="tok-punct">]</span>
<span class="tok-name">prep</span> <span class="tok-operator">=</span> <span class="tok-builtin">dict</span><span class="tok-punct">[</span><span class="tok-string">'Prep'</span><span class="tok-punct">]</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span>f'<span class="tok-punct">{</span><span class="tok-name">ingredient</span><span class="tok-punct">}</span>: (<span class="tok-punct">{</span><span class="tok-name">amount</span><span class="tok-punct">}</span>) - <span class="tok-punct">{</span><span class="tok-name">prep</span><span class="tok-punct">}</span>'<span class="tok-punct">)</span>
<span class="tok-comment"># Python allows us to write to CSV files just as easily with the csv module</span>
<span class="tok-comment"># Notice how we can use keyword parameters to set the delimiter to a pipe (|) instead of a comma</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'hotdish_recipe.psv'</span><span class="tok-punct">,</span><span class="tok-string">'w'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">output_file</span><span class="tok-punct">:</span>
<span class="tok-name">schema</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-string">'Ingredient'</span><span class="tok-punct">,</span><span class="tok-string">'Amount'</span><span class="tok-punct">,</span><span class="tok-string">'Prep'</span><span class="tok-punct">]</span>
<span class="tok-name">data</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span>
<span class="tok-punct">{</span><span class="tok-string">'Ingredient'</span><span class="tok-punct">:</span><span class="tok-string">'beef'</span><span class="tok-punct">,</span><span class="tok-string">'Amount'</span><span class="tok-punct">:</span><span class="tok-string">'2 lbs'</span><span class="tok-punct">,</span><span class="tok-string">'Prep'</span><span class="tok-punct">:</span><span class="tok-string">'Thaw, cook then set aside'</span><span class="tok-punct">}</span><span class="tok-punct">,</span>
<span class="tok-punct">{</span><span class="tok-string">'Ingredient'</span><span class="tok-punct">:</span><span class="tok-string">'Potatoes'</span><span class="tok-punct">,</span><span class="tok-string">'Amount'</span><span class="tok-punct">:</span><span class="tok-string">'12 large'</span><span class="tok-punct">,</span><span class="tok-string">'Prep'</span><span class="tok-punct">:</span><span class="tok-string">'Skin, boil, mash then let cool'</span><span class="tok-punct">}</span><span class="tok-punct">,</span>
<span class="tok-punct">{</span><span class="tok-string">'Ingredient'</span><span class="tok-punct">:</span><span class="tok-string">'Cream'</span><span class="tok-punct">,</span><span class="tok-string">'Amount'</span><span class="tok-punct">:</span><span class="tok-string">'2 cups'</span><span class="tok-punct">,</span><span class="tok-string">'Prep'</span><span class="tok-punct">:</span><span class="tok-string">'Warm then stir into beef and potatoes'</span><span class="tok-punct">}</span>
<span class="tok-punct">]</span>
<span class="tok-name">csv_writer</span> <span class="tok-operator">=</span> <span class="tok-name">csv</span><span class="tok-punct">.</span><span class="tok-name">DictWriter</span><span class="tok-punct">(</span><span class="tok-name">output_file</span><span class="tok-punct">,</span><span class="tok-name">schema</span><span class="tok-punct">,</span><span class="tok-name">delimiter</span><span class="tok-operator">=</span><span class="tok-string">'|'</span><span class="tok-punct">,</span><span class="tok-name">lineterminator</span><span class="tok-operator">=</span><span class="tok-string">'\n'</span><span class="tok-punct">)</span>
<span class="tok-name">csv_writer</span><span class="tok-punct">.</span><span class="tok-name">writeheader</span><span class="tok-punct">(</span><span class="tok-punct">)</span>
<span class="tok-keyword">for</span> <span class="tok-name">item</span> <span class="tok-keyword">in</span> <span class="tok-name">data</span><span class="tok-punct">:</span>
<span class="tok-name">csv_writer</span><span class="tok-punct">.</span><span class="tok-name">writerow</span><span class="tok-punct">(</span><span class="tok-name">item</span><span class="tok-punct">)</span>
<span class="tok-comment"># This example above is not the most efficient method. The data variable is a List of Dictionaries which works well</span>
<span class="tok-comment"># but relies on the header values being duplicated on each row.</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># File System: JSON Format #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python also supports reading and writing JSON data with the json module</span>
<span class="tok-comment"># Let's create some sample data for the next examples</span>
<span class="tok-keyword">def</span> <span class="tok-name">json_payload</span><span class="tok-punct">(</span><span class="tok-name">data</span><span class="tok-punct">:</span> <span class="tok-builtin">str</span><span class="tok-punct">)</span> <span class="tok-operator">-></span> <span class="tok-keyword">None</span><span class="tok-punct">:</span> <span class="tok-comment"># : str and -> None are called type hints</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'python_primer.json'</span><span class="tok-punct">,</span><span class="tok-string">'w'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">json_file</span><span class="tok-punct">:</span>
<span class="tok-name">json_file</span><span class="tok-punct">.</span><span class="tok-name">write</span><span class="tok-punct">(</span><span class="tok-name">data</span><span class="tok-punct">)</span>
<span class="tok-comment"># Python's json module has a load function which will read JSON from disk and output a data</span>
<span class="tok-comment"># structure for us from the contents</span>
<span class="tok-name">json_payload</span><span class="tok-punct">(</span><span class="tok-string">'{"hello":"world"}'</span><span class="tok-punct">)</span> <span class="tok-comment"># Save some JSON to disk</span>
<span class="tok-keyword">from</span> <span class="tok-name">json</span> <span class="tok-keyword">import</span> <span class="tok-name">load</span> <span class="tok-keyword">as</span> <span class="tok-name">json_load</span> <span class="tok-comment"># Import the load function from json as json_load</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'python_primer.json'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">json_file</span><span class="tok-punct">:</span> <span class="tok-comment"># Open the JSON file in read mode</span>
<span class="tok-name">json_data</span> <span class="tok-operator">=</span> <span class="tok-name">json_load</span><span class="tok-punct">(</span><span class="tok-name">json_file</span><span class="tok-punct">)</span> <span class="tok-comment"># Load the JSON into a variable</span>
<span class="tok-comment"># Python's json module returns JSON data in a list or dictionary format depending on the</span>
<span class="tok-comment"># schema of the JSON itself</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'Hello, {}!'</span><span class="tok-punct">.</span><span class="tok-builtin">format</span><span class="tok-punct">(</span><span class="tok-name">json_data</span><span class="tok-punct">[</span><span class="tok-string">'hello'</span><span class="tok-punct">]</span><span class="tok-punct">)</span><span class="tok-punct">)</span>
<span class="tok-comment"># Let's define json_get so we don't have to copy the JSON read code over and over again for the next examples</span>
<span class="tok-keyword">def</span> <span class="tok-name">json_get</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">:</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-string">'python_primer.json'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">json_file</span><span class="tok-punct">:</span>
<span class="tok-keyword">return</span> <span class="tok-name">json_load</span><span class="tok-punct">(</span><span class="tok-name">json_file</span><span class="tok-punct">)</span>
<span class="tok-comment"># Let's show some other examples of how Python processes JSON</span>
<span class="tok-name">json_payload</span><span class="tok-punct">(</span><span class="tok-string">'[{"hello":"world"}]'</span><span class="tok-punct">)</span> <span class="tok-comment"># This JSON is an array of objects</span>
<span class="tok-name">json_output</span> <span class="tok-operator">=</span> <span class="tok-name">json_get</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Python returns a List with one Dictonary item</span>
<span class="tok-name">json_output</span><span class="tok-punct">[</span><span class="tok-number">0</span><span class="tok-punct">]</span><span class="tok-punct">[</span><span class="tok-string">'hello'</span><span class="tok-punct">]</span>
<span class="tok-name">json_payload</span><span class="tok-punct">(</span><span class="tok-string">'{"hello":{"place":"world"}}'</span><span class="tok-punct">)</span> <span class="tok-comment"># This JSON is an object with a subobject</span>
<span class="tok-name">json_output</span> <span class="tok-operator">=</span> <span class="tok-name">json_get</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Python returns a Dictionary with one Dictionary value</span>
<span class="tok-name">json_output</span><span class="tok-punct">[</span><span class="tok-string">'hello'</span><span class="tok-punct">]</span><span class="tok-punct">[</span><span class="tok-string">'place'</span><span class="tok-punct">]</span>
<span class="tok-name">json_payload</span><span class="tok-punct">(</span><span class="tok-string">'{"hello":[{"place":"world"}]}'</span><span class="tok-punct">)</span> <span class="tok-comment"># This JSON is an object with a subarray of objects</span>
<span class="tok-name">json_output</span> <span class="tok-operator">=</span> <span class="tok-name">json_get</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Python returns a Dictionary with one List value of Dictionary type</span>
<span class="tok-name">json_output</span><span class="tok-punct">[</span><span class="tok-string">'hello'</span><span class="tok-punct">]</span><span class="tok-punct">[</span><span class="tok-number">0</span><span class="tok-punct">]</span><span class="tok-punct">[</span><span class="tok-string">'place'</span><span class="tok-punct">]</span>
<span class="tok-comment"># What you'll notice about Python and JSON is how Python deserializes native JSON into native Python</span>
<span class="tok-comment"># data structures. Any JSON can be expressed as a Dictionary, List, or Dictionary of Lists or</span>
<span class="tok-comment"># List of Dictionaries.</span>
<span class="tok-comment"># Conversely, the JSON module let's us serialize native Python Dictionary and List types to JSON</span>
<span class="tok-keyword">from</span> <span class="tok-name">json</span> <span class="tok-keyword">import</span> <span class="tok-name">dump</span>
<span class="tok-keyword">def</span> <span class="tok-name">json_out</span><span class="tok-punct">(</span><span class="tok-name">data</span><span class="tok-punct">,</span><span class="tok-name">filename</span><span class="tok-punct">:</span> <span class="tok-builtin">str</span> <span class="tok-operator">=</span> <span class="tok-string">'python_primer.json'</span><span class="tok-punct">)</span><span class="tok-punct">:</span>
<span class="tok-keyword">with</span> <span class="tok-builtin">open</span><span class="tok-punct">(</span><span class="tok-name">filename</span><span class="tok-punct">,</span><span class="tok-string">'w'</span><span class="tok-punct">)</span> <span class="tok-keyword">as</span> <span class="tok-name">json_file</span><span class="tok-punct">:</span>
<span class="tok-name">dump</span><span class="tok-punct">(</span><span class="tok-name">data</span><span class="tok-punct">,</span><span class="tok-name">json_file</span><span class="tok-punct">)</span> <span class="tok-comment"># The dump function writes JSON to a file from an object</span>
<span class="tok-comment"># We can now write various Python data structures out to native JSON</span>
<span class="tok-name">list_of_letters</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-string">'a'</span><span class="tok-punct">,</span><span class="tok-string">'b'</span><span class="tok-punct">,</span><span class="tok-string">'c'</span><span class="tok-punct">,</span><span class="tok-string">'d'</span><span class="tok-punct">,</span><span class="tok-string">'e'</span><span class="tok-punct">,</span><span class="tok-string">'f'</span><span class="tok-punct">,</span><span class="tok-string">'g'</span><span class="tok-punct">,</span><span class="tok-string">'h'</span><span class="tok-punct">,</span><span class="tok-string">'i'</span><span class="tok-punct">,</span><span class="tok-string">'j'</span><span class="tok-punct">,</span><span class="tok-string">'k'</span><span class="tok-punct">,</span><span class="tok-string">'l'</span><span class="tok-punct">]</span> <span class="tok-comment"># Serialized as-is</span>
<span class="tok-name">list_of_tuples</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-punct">(</span><span class="tok-string">'a'</span><span class="tok-punct">,</span><span class="tok-string">'b'</span><span class="tok-punct">)</span><span class="tok-punct">,</span><span class="tok-punct">(</span><span class="tok-string">'c'</span><span class="tok-punct">,</span><span class="tok-string">'d'</span><span class="tok-punct">)</span><span class="tok-punct">,</span><span class="tok-punct">(</span><span class="tok-string">'e'</span><span class="tok-punct">,</span><span class="tok-string">'f'</span><span class="tok-punct">)</span><span class="tok-punct">,</span><span class="tok-punct">(</span><span class="tok-string">'g'</span><span class="tok-punct">,</span><span class="tok-string">'h'</span><span class="tok-punct">)</span><span class="tok-punct">]</span> <span class="tok-comment"># Tuples are serialized as arrays</span>
<span class="tok-name">list_of_dictionaries</span> <span class="tok-operator">=</span> <span class="tok-punct">[</span><span class="tok-punct">{</span><span class="tok-string">'a'</span><span class="tok-punct">:</span><span class="tok-string">'b'</span><span class="tok-punct">}</span><span class="tok-punct">,</span><span class="tok-punct">{</span><span class="tok-string">'c'</span><span class="tok-punct">:</span><span class="tok-string">'d'</span><span class="tok-punct">}</span><span class="tok-punct">,</span><span class="tok-punct">{</span><span class="tok-string">'e'</span><span class="tok-punct">:</span><span class="tok-string">'f'</span><span class="tok-punct">}</span><span class="tok-punct">,</span><span class="tok-punct">{</span><span class="tok-string">'g'</span><span class="tok-punct">:</span><span class="tok-string">'h'</span><span class="tok-punct">}</span><span class="tok-punct">]</span> <span class="tok-comment"># Serialized as a list of objects</span>
<span class="tok-name">dictionary_of_lists</span> <span class="tok-operator">=</span> <span class="tok-punct">{</span><span class="tok-string">'a'</span><span class="tok-punct">:</span><span class="tok-punct">[</span><span class="tok-string">'b'</span><span class="tok-punct">,</span><span class="tok-string">'c'</span><span class="tok-punct">,</span><span class="tok-string">'d'</span><span class="tok-punct">]</span><span class="tok-punct">,</span><span class="tok-string">'e'</span><span class="tok-punct">:</span><span class="tok-punct">[</span><span class="tok-string">'f'</span><span class="tok-punct">,</span><span class="tok-string">'g'</span><span class="tok-punct">,</span><span class="tok-string">'h'</span><span class="tok-punct">]</span><span class="tok-punct">}</span> <span class="tok-comment"># Serialized as an object with array properties</span>
<span class="tok-name">dictionary_of_dictionaries</span> <span class="tok-operator">=</span> <span class="tok-punct">{</span><span class="tok-string">'a'</span><span class="tok-punct">:</span><span class="tok-punct">{</span><span class="tok-string">'b'</span><span class="tok-punct">:</span><span class="tok-string">'c'</span><span class="tok-punct">}</span><span class="tok-punct">,</span><span class="tok-string">'d'</span><span class="tok-punct">:</span><span class="tok-punct">{</span><span class="tok-string">'e'</span><span class="tok-punct">:</span><span class="tok-string">'f'</span><span class="tok-punct">}</span><span class="tok-punct">,</span><span class="tok-string">'g'</span><span class="tok-punct">:</span><span class="tok-punct">{</span><span class="tok-string">'h'</span><span class="tok-punct">:</span><span class="tok-string">'i'</span><span class="tok-punct">}</span><span class="tok-punct">}</span> <span class="tok-comment"># Serialized as an object with object properties</span>
<span class="tok-name">json_out</span><span class="tok-punct">(</span><span class="tok-name">list_of_letters</span><span class="tok-punct">,</span><span class="tok-string">'py_list_of_letters.json'</span><span class="tok-punct">)</span>
<span class="tok-name">json_out</span><span class="tok-punct">(</span><span class="tok-name">list_of_tuples</span><span class="tok-punct">,</span><span class="tok-string">'py_list_of_tuples.json'</span><span class="tok-punct">)</span>
<span class="tok-name">json_out</span><span class="tok-punct">(</span><span class="tok-name">list_of_dictionaries</span><span class="tok-punct">,</span><span class="tok-string">'py_list_of_dictionaries.json'</span><span class="tok-punct">)</span>
<span class="tok-name">json_out</span><span class="tok-punct">(</span><span class="tok-name">dictionary_of_lists</span><span class="tok-punct">,</span><span class="tok-string">'py_dictionary_of_lists.json'</span><span class="tok-punct">)</span>
<span class="tok-name">json_out</span><span class="tok-punct">(</span><span class="tok-name">dictionary_of_dictionaries</span><span class="tok-punct">,</span><span class="tok-string">'py_dictionary_of_dictionaries.json'</span><span class="tok-punct">)</span>
<span class="tok-comment"># In Python, any serializable object can be written into JSON</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># 6. Classes #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># Python is a typed language, every object in Python has a type which you can get using the type function</span>
<span class="tok-builtin">type</span><span class="tok-punct">(</span><span class="tok-number">5</span><span class="tok-punct">)</span> <span class="tok-comment"># 5 is an int</span>
<span class="tok-builtin">type</span><span class="tok-punct">(</span><span class="tok-string">'five'</span><span class="tok-punct">)</span> <span class="tok-comment"># 'five is an str (String)</span>
<span class="tok-builtin">type</span><span class="tok-punct">(</span><span class="tok-punct">[</span><span class="tok-number">5</span><span class="tok-punct">,</span><span class="tok-string">'five'</span><span class="tok-punct">]</span><span class="tok-punct">)</span> <span class="tok-comment"># [] is a List</span>
<span class="tok-builtin">type</span><span class="tok-punct">(</span><span class="tok-punct">{</span><span class="tok-number">5</span><span class="tok-punct">:</span><span class="tok-string">'five'</span><span class="tok-punct">}</span><span class="tok-punct">)</span> <span class="tok-comment"># {} is a Dictionary</span>
<span class="tok-builtin">type</span><span class="tok-punct">(</span><span class="tok-punct">(</span><span class="tok-string">'five'</span><span class="tok-punct">,</span><span class="tok-number">5</span><span class="tok-punct">)</span><span class="tok-punct">)</span> <span class="tok-comment"># () is a Tuple</span>
<span class="tok-builtin">type</span><span class="tok-punct">(</span><span class="tok-punct">{</span><span class="tok-string">'five'</span><span class="tok-punct">,</span><span class="tok-string">'six'</span><span class="tok-punct">,</span><span class="tok-string">'seven'</span><span class="tok-punct">}</span><span class="tok-punct">)</span> <span class="tok-comment"># {1,2,3} is a Set</span>
<span class="tok-comment"># Python allows you to check run-time types using the is keyword</span>
<span class="tok-keyword">if</span> <span class="tok-builtin">type</span><span class="tok-punct">(</span><span class="tok-number">5</span><span class="tok-punct">)</span> <span class="tok-keyword">is</span> <span class="tok-builtin">int</span><span class="tok-punct">:</span> <span class="tok-builtin">print</span><span class="tok-punct">(</span>f'5 is an int'<span class="tok-punct">)</span>
<span class="tok-comment"># The defined type of an object is called its class</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># User-Defined Classes #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># In Python, like in many languages, every object has a type and the class keyword lets you define your own</span>
<span class="tok-keyword">class</span> <span class="tok-name">Person</span><span class="tok-punct">:</span> <span class="tok-comment"># The class keyword defines a class by name</span>
<span class="tok-name">name</span> <span class="tok-operator">=</span> <span class="tok-string">'George Costanza'</span> <span class="tok-comment"># Variables at the class scope are called attributes</span>
<span class="tok-keyword">def</span> <span class="tok-name">__init__</span><span class="tok-punct">(</span><span class="tok-name">self</span><span class="tok-punct">,</span><span class="tok-name">name</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-comment"># The __init__ dunder method defines the constructor</span>
<span class="tok-name">self</span><span class="tok-punct">.</span><span class="tok-name">name</span> <span class="tok-operator">=</span> <span class="tok-name">name</span> <span class="tok-comment"># The new instance itself must always be the first argument</span>
<span class="tok-keyword">def</span> <span class="tok-name">__repr__</span><span class="tok-punct">(</span><span class="tok-name">self</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-comment"># The dunder method that converts this to a string</span>
<span class="tok-keyword">return</span> <span class="tok-name">self</span><span class="tok-punct">.</span><span class="tok-name">name</span> <span class="tok-comment"># Python classes have many dunder methods (built-ins)</span>
<span class="tok-keyword">def</span> <span class="tok-name">greet</span><span class="tok-punct">(</span><span class="tok-name">self</span><span class="tok-punct">,</span><span class="tok-name">greeter</span><span class="tok-punct">:</span> <span class="tok-name">Person</span><span class="tok-punct">)</span> <span class="tok-operator">-></span> <span class="tok-builtin">str</span><span class="tok-punct">:</span> <span class="tok-comment"># This is an instance method, note how self is an argument</span>
<span class="tok-keyword">return</span> f'Hello, <span class="tok-punct">{</span><span class="tok-name">greeter</span><span class="tok-punct">.</span><span class="tok-name">name</span><span class="tok-punct">}</span>. My name is <span class="tok-punct">{</span><span class="tok-name">self</span><span class="tok-punct">.</span><span class="tok-name">name</span><span class="tok-punct">}</span>.' <span class="tok-comment"># self is not an ephemeral variable like 'this' in other</span>
<span class="tok-comment"># object-oriented languages, it must be declared</span>
<span class="tok-keyword">def</span> <span class="tok-name">sayhello</span><span class="tok-punct">(</span><span class="tok-name">this</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-comment"># The fun part is that 'self' is not a keyword, it's only</span>
<span class="tok-keyword">return</span> f'Hello, my name is <span class="tok-punct">{</span><span class="tok-name">this</span><span class="tok-punct">.</span><span class="tok-name">name</span><span class="tok-punct">}</span>.' <span class="tok-comment"># a convention, so you can technically use any name for</span>
<span class="tok-comment"># the argument to reference the current instance</span>
<span class="tok-keyword">def</span> <span class="tok-name">echo</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-comment"># Every instance method of a class is required to have 1 argument and that one first argument will</span>
<span class="tok-keyword">return</span> <span class="tok-string">'Hello'</span> <span class="tok-comment"># always be set to the instance of the class itself calling the method. This method definition, while</span>
<span class="tok-comment"># it can be defined, will actually throw a TypeError if you try to invoke it because the run-time is</span>
<span class="tok-comment"># passing the instance of itself as the first argument automatically, but this definition does not</span>
<span class="tok-comment"># accept any arguments at all.</span>
<span class="tok-comment"># The class definition ends when we outdent back to the local namespace</span>
<span class="tok-comment"># Let's instantiate some instances of our new class and do things with them</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># User-Defined Class Variables #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python lets you declare & create (instantiate) any class you define by "calling" the class like a function</span>
<span class="tok-comment"># This calls the __init__ method on the class and gives you a new instance of the class</span>
<span class="tok-name">alice</span> <span class="tok-operator">=</span> <span class="tok-name">Person</span><span class="tok-punct">(</span><span class="tok-string">'Alice'</span><span class="tok-punct">)</span> <span class="tok-comment"># Make a new Person named Alice</span>
<span class="tok-name">bob</span> <span class="tok-operator">=</span> <span class="tok-name">Person</span><span class="tok-punct">(</span><span class="tok-string">'Bob'</span><span class="tok-punct">)</span> <span class="tok-comment"># Make a new Person named Bob</span>
<span class="tok-comment"># Python lets you access class attributes and call methods using the dot (.) operator</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">alice</span><span class="tok-punct">.</span><span class="tok-name">sayhello</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">)</span> <span class="tok-comment"># Make Alice say Hello</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">bob</span><span class="tok-punct">.</span><span class="tok-name">sayhello</span><span class="tok-punct">(</span><span class="tok-punct">)</span><span class="tok-punct">)</span> <span class="tok-comment"># Make Bob say Hello</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">alice</span><span class="tok-punct">.</span><span class="tok-name">greet</span><span class="tok-punct">(</span><span class="tok-name">bob</span><span class="tok-punct">)</span><span class="tok-punct">)</span> <span class="tok-comment"># Have Alice greet Bob</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">bob</span><span class="tok-punct">.</span><span class="tok-name">greet</span><span class="tok-punct">(</span><span class="tok-name">alice</span><span class="tok-punct">)</span><span class="tok-punct">)</span> <span class="tok-comment"># Have Bob greet Alice</span>
<span class="tok-comment"># alice.echo() # If you try to run this, you'll generate a TypeError because echo() has no arguments</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Attribute Testing #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Python run-time allows you to test objects for their attributes to avoid run-time errors</span>
<span class="tok-name">alice</span><span class="tok-punct">.</span><span class="tok-name">name</span> <span class="tok-operator">=</span> <span class="tok-string">'Alice'</span> <span class="tok-comment"># Our class Person has a name attribute</span>
<span class="tok-builtin">hasattr</span><span class="tok-punct">(</span><span class="tok-name">alice</span><span class="tok-punct">,</span><span class="tok-string">'name'</span><span class="tok-punct">)</span> <span class="tok-comment"># We can test for it using the hasattr function</span>
<span class="tok-builtin">getattr</span><span class="tok-punct">(</span><span class="tok-name">alice</span><span class="tok-punct">,</span><span class="tok-string">'name'</span><span class="tok-punct">)</span> <span class="tok-comment"># We can use the getattr function to get alice.name</span>
<span class="tok-builtin">getattr</span><span class="tok-punct">(</span><span class="tok-name">alice</span><span class="tok-punct">,</span><span class="tok-string">'name'</span><span class="tok-punct">,</span><span class="tok-string">'Alice'</span><span class="tok-punct">)</span> <span class="tok-comment"># This is useful if we don't know if alice has a name, we can get a default value instead</span>
<span class="tok-comment"># Python provides a directory list using the dir function allowing you to get every attribute in a List</span>
<span class="tok-name">scope_list</span> <span class="tok-operator">=</span> <span class="tok-builtin">dir</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Gets every attribute in the current scope</span>
<span class="tok-name">person_list</span> <span class="tok-operator">=</span> <span class="tok-builtin">dir</span><span class="tok-punct">(</span><span class="tok-name">alice</span><span class="tok-punct">)</span> <span class="tok-comment"># Gets every attribute of the alice instance of Person</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-punct">[</span><span class="tok-name">a</span> <span class="tok-keyword">for</span> <span class="tok-name">a</span> <span class="tok-keyword">in</span> <span class="tok-builtin">dir</span><span class="tok-punct">(</span><span class="tok-name">alice</span><span class="tok-punct">)</span> <span class="tok-keyword">if</span> <span class="tok-name">a</span><span class="tok-punct">.</span><span class="tok-name">find</span><span class="tok-punct">(</span><span class="tok-string">'__'</span><span class="tok-punct">)</span> <span class="tok-operator"><</span> <span class="tok-number">0</span><span class="tok-punct">]</span><span class="tok-punct">)</span> <span class="tok-comment"># A List Comprehension removing dunder methods so we can find all the</span>
<span class="tok-comment"># user-defined attributes and methods of a Person</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Type Hints #</span>
<span class="tok-comment"># ###################################################### #</span>
<span class="tok-comment"># Up until now we have been defining functions with simple declaration statements</span>
<span class="tok-keyword">def</span> <span class="tok-name">add_two_numbers</span><span class="tok-punct">(</span><span class="tok-name">a</span><span class="tok-punct">,</span><span class="tok-name">b</span><span class="tok-punct">)</span><span class="tok-punct">:</span> <span class="tok-comment"># We expect two numbers, but that's not explicitly stated</span>
<span class="tok-keyword">return</span> <span class="tok-name">a</span> <span class="tok-operator">+</span> <span class="tok-name">b</span> <span class="tok-comment"># We add them together and return the result</span>
<span class="tok-comment"># This won't behave as expected if a or b are not a number</span>
<span class="tok-comment"># Type hints allow the Python interpreter to tell the developer what type is expected</span>
<span class="tok-keyword">def</span> <span class="tok-name">add_two_numbers</span><span class="tok-punct">(</span><span class="tok-name">a</span><span class="tok-punct">:</span> <span class="tok-builtin">int</span><span class="tok-punct">,</span> <span class="tok-name">b</span><span class="tok-punct">:</span> <span class="tok-builtin">int</span><span class="tok-punct">)</span> <span class="tok-operator">-></span> <span class="tok-builtin">int</span><span class="tok-punct">:</span> <span class="tok-comment"># Here we use type hints to tell the developer that we</span>
<span class="tok-keyword">return</span> <span class="tok-name">a</span> <span class="tok-operator">+</span> <span class="tok-name">b</span> <span class="tok-comment"># are expecting integers for a and b and that we'll be</span>
<span class="tok-comment"># returning an integer as well</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># 7. Error Handling #</span>
<span class="tok-comment"># #</span>
<span class="tok-comment"># ################################################################################################# #</span>
<span class="tok-comment"># Python, like most languages, allows you to trap run-time errors at run-time using the try/except syntax</span>
<span class="tok-keyword">try</span><span class="tok-punct">:</span>
<span class="tok-name">alice</span><span class="tok-punct">.</span><span class="tok-name">echo</span><span class="tok-punct">(</span><span class="tok-punct">)</span> <span class="tok-comment"># Let's call our broken method on the Person class</span>
<span class="tok-keyword">except</span> <span class="tok-builtin">TypeError</span><span class="tok-punct">:</span> <span class="tok-comment"># Here we define the expected error TypeError</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'alice.echo() generated expected TypeError'</span><span class="tok-punct">)</span> <span class="tok-comment"># This will run if alice.echo() generates a TypeError</span>
<span class="tok-comment"># and the TypeError will not stop our script</span>
<span class="tok-comment"># Your code can also raise errors using the raise keyword if you need to halt execution</span>
<span class="tok-keyword">try</span><span class="tok-punct">:</span>
<span class="tok-keyword">raise</span> <span class="tok-builtin">NameError</span><span class="tok-punct">(</span><span class="tok-name">name</span><span class="tok-operator">=</span><span class="tok-string">'kwyjibo'</span><span class="tok-punct">)</span>
<span class="tok-keyword">except</span><span class="tok-punct">:</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'Caught error'</span><span class="tok-punct">)</span>
<span class="tok-comment"># Finally, here is an example of a full try/except block with all possible operations</span>
<span class="tok-comment"># Except blocks are not mutually exclusive, both except blocks below will execute because</span>
<span class="tok-comment"># the error raised is a NameError, so the NameError block runs, and the any error block</span>
<span class="tok-comment"># also runs. This is by design.</span>
<span class="tok-keyword">try</span><span class="tok-punct">:</span> <span class="tok-comment"># Here we initiate the error trap</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-name">kwyjibo</span><span class="tok-punct">)</span>
<span class="tok-keyword">except</span> <span class="tok-builtin">NameError</span><span class="tok-punct">:</span> <span class="tok-comment"># Here we trap a specific NameError</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'Caught NameError'</span><span class="tok-punct">)</span>
<span class="tok-keyword">except</span><span class="tok-punct">:</span> <span class="tok-comment"># Here we trap any error, regardless of type</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'Caught error'</span><span class="tok-punct">)</span>
<span class="tok-keyword">else</span><span class="tok-punct">:</span> <span class="tok-comment"># Here we run some code if there were no errors</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'No error'</span><span class="tok-punct">)</span>
<span class="tok-keyword">finally</span><span class="tok-punct">:</span> <span class="tok-comment"># And finally, we always run this code to make sure everything is cleaned up</span>
<span class="tok-builtin">print</span><span class="tok-punct">(</span><span class="tok-string">'Always runs, for cleanup of issues/open handles, etc.'</span><span class="tok-punct">)</span></code></pre>
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