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<li><a href="#diving-in" id="toc-diving-in" class="nav-link" data-scroll-target="#diving-in">Diving In</a></li>
<li><a href="#motivating-example" id="toc-motivating-example" class="nav-link" data-scroll-target="#motivating-example">Motivating Example</a></li>
<li><a href="#is-this-real" id="toc-is-this-real" class="nav-link" data-scroll-target="#is-this-real">Is this “real”?</a></li>
<li><a href="#how-to-solve" id="toc-how-to-solve" class="nav-link" data-scroll-target="#how-to-solve">How to solve?</a></li>
<li><a href="#python-in-action" id="toc-python-in-action" class="nav-link" data-scroll-target="#python-in-action">Python in action</a></li>
<li><a href="#arithmetic-operations" id="toc-arithmetic-operations" class="nav-link" data-scroll-target="#arithmetic-operations">Arithmetic Operations</a></li>
</ul></li>
<li><a href="#evaluating-expressions" id="toc-evaluating-expressions" class="nav-link" data-scroll-target="#evaluating-expressions">Evaluating Expressions</a>
<ul class="collapse">
<li><a href="#recall" id="toc-recall" class="nav-link" data-scroll-target="#recall">Recall</a></li>
<li><a href="#inequality-testing" id="toc-inequality-testing" class="nav-link" data-scroll-target="#inequality-testing">(In)equality testing</a></li>
<li><a href="#accomodating-keyboards" id="toc-accomodating-keyboards" class="nav-link" data-scroll-target="#accomodating-keyboards">Accomodating Keyboards</a></li>
<li><a href="#a-note" id="toc-a-note" class="nav-link" data-scroll-target="#a-note">A note</a></li>
</ul></li>
<li><a href="#and" id="toc-and" class="nav-link" data-scroll-target="#and"><code>=</code> and <code>==</code></a>
<ul class="collapse">
<li><a href="#new-topics" id="toc-new-topics" class="nav-link" data-scroll-target="#new-topics">New Topics</a></li>
<li><a href="#booleans" id="toc-booleans" class="nav-link" data-scroll-target="#booleans">Booleans</a></li>
<li><a href="#if" id="toc-if" class="nav-link" data-scroll-target="#if">If</a></li>
<li><a href="#piecewise" id="toc-piecewise" class="nav-link" data-scroll-target="#piecewise">Piecewise</a></li>
<li><a href="#else" id="toc-else" class="nav-link" data-scroll-target="#else">Else</a></li>
<li><a href="#elif" id="toc-elif" class="nav-link" data-scroll-target="#elif">Elif</a></li>
<li><a href="#assignment" id="toc-assignment" class="nav-link" data-scroll-target="#assignment">Assignment</a></li>
<li><a href="#double-equals-equality" id="toc-double-equals-equality" class="nav-link" data-scroll-target="#double-equals-equality">Double equals equality</a></li>
<li><a href="#double-exponentation" id="toc-double-exponentation" class="nav-link" data-scroll-target="#double-exponentation">Double ** Exponentation</a></li>
<li><a href="#piecewise-1" id="toc-piecewise-1" class="nav-link" data-scroll-target="#piecewise-1">Piecewise</a></li>
</ul></li>
<li><a href="#code-reuse" id="toc-code-reuse" class="nav-link" data-scroll-target="#code-reuse">Code Reuse</a>
<ul class="collapse">
<li><a href="#recycle" id="toc-recycle" class="nav-link" data-scroll-target="#recycle">Recycle</a></li>
<li><a href="#def" id="toc-def" class="nav-link" data-scroll-target="#def"><code>def</code></a></li>
<li><a href="#metaphor" id="toc-metaphor" class="nav-link" data-scroll-target="#metaphor">Metaphor</a></li>
<li><a href="#return" id="toc-return" class="nav-link" data-scroll-target="#return"><code>return</code></a></li>
<li><a href="#example-1" id="toc-example-1" class="nav-link" data-scroll-target="#example-1">Example</a></li>
<li><a href="#use-return" id="toc-use-return" class="nav-link" data-scroll-target="#use-return">Use return</a></li>
<li><a href="#piecewise-2" id="toc-piecewise-2" class="nav-link" data-scroll-target="#piecewise-2">Piecewise</a></li>
</ul></li>
<li><a href="#iteration" id="toc-iteration" class="nav-link" data-scroll-target="#iteration">Iteration</a>
<ul class="collapse">
<li><a href="#tedium" id="toc-tedium" class="nav-link" data-scroll-target="#tedium">Tedium</a></li>
<li><a href="#sets" id="toc-sets" class="nav-link" data-scroll-target="#sets">Sets</a></li>
<li><a href="#type" id="toc-type" class="nav-link" data-scroll-target="#type">Type</a></li>
<li><a href="#loops" id="toc-loops" class="nav-link" data-scroll-target="#loops">Loops</a></li>
<li><a href="#example-2" id="toc-example-2" class="nav-link" data-scroll-target="#example-2">Example</a></li>
<li><a href="#example-3" id="toc-example-3" class="nav-link" data-scroll-target="#example-3">Example</a></li>
<li><a href="#ordering" id="toc-ordering" class="nav-link" data-scroll-target="#ordering">Ordering</a></li>
<li><a href="#example-4" id="toc-example-4" class="nav-link" data-scroll-target="#example-4">Example</a></li>
<li><a href="#seeing-lists" id="toc-seeing-lists" class="nav-link" data-scroll-target="#seeing-lists">Seeing lists</a></li>
<li><a href="#updating-lists" id="toc-updating-lists" class="nav-link" data-scroll-target="#updating-lists">Updating lists</a></li>
<li><a href="#metaphor-1" id="toc-metaphor-1" class="nav-link" data-scroll-target="#metaphor-1">Metaphor</a></li>
<li><a href="#adding-lists" id="toc-adding-lists" class="nav-link" data-scroll-target="#adding-lists">Adding lists</a></li>
<li><a href="#careful" id="toc-careful" class="nav-link" data-scroll-target="#careful">Careful!</a></li>
</ul></li>
<li><a href="#exercise" id="toc-exercise" class="nav-link" data-scroll-target="#exercise">Exercise</a>
<ul class="collapse">
<li><a href="#income-tax" id="toc-income-tax" class="nav-link" data-scroll-target="#income-tax">Income tax</a></li>
<li><a href="#singles-only" id="toc-singles-only" class="nav-link" data-scroll-target="#singles-only">Singles only…</a></li>
<li><a href="#motivating-example-1" id="toc-motivating-example-1" class="nav-link" data-scroll-target="#motivating-example-1">Motivating example</a></li>
<li><a href="#sum-it-up" id="toc-sum-it-up" class="nav-link" data-scroll-target="#sum-it-up">Sum it up!</a></li>
<li><a href="#add-as-you-go" id="toc-add-as-you-go" class="nav-link" data-scroll-target="#add-as-you-go">Add as you go</a></li>
<li><a href="#assign-update" id="toc-assign-update" class="nav-link" data-scroll-target="#assign-update">Assign-update</a></li>
<li><a href="#exercise-1" id="toc-exercise-1" class="nav-link" data-scroll-target="#exercise-1">Exercise</a></li>
<li><a href="#solution" id="toc-solution" class="nav-link" data-scroll-target="#solution">Solution</a></li>
<li><a href="#challenge-problem" id="toc-challenge-problem" class="nav-link" data-scroll-target="#challenge-problem">Challenge Problem</a></li>
<li><a href="#bonus-solution" id="toc-bonus-solution" class="nav-link" data-scroll-target="#bonus-solution">Bonus Solution</a></li>
</ul></li>
</ul>
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<div class="quarto-title">
<div class="quarto-title-block"><div><h1 class="title">Python</h1><button type="button" class="btn code-tools-button" id="quarto-code-tools-source"><i class="bi"></i></button></div></div>
<p class="subtitle lead">Thinking Machines</p>
</div>
<div class="quarto-title-meta">
<div>
<div class="quarto-title-meta-heading">Author</div>
<div class="quarto-title-meta-contents">
<p>Prof. Calvin </p>
</div>
</div>
</div>
</header>
<section id="installing-python" class="level1">
<h1>Installing Python</h1>
<section id="warning" class="level2">
<h2 class="anchored" data-anchor-id="warning">Warning!</h2>
<ul>
<li>There is a very important box to check while installing!
<ul>
<li>Be careful working ahead!</li>
<li>We’ll teach how to fix not checking this box <em>but not for a while</em></li>
</ul></li>
</ul>
</section>
<section id="installation" class="level2">
<h2 class="anchored" data-anchor-id="installation">Installation</h2>
<ul>
<li>We go to the offial webpage to get an installer for our computer:
<ul>
<li><a href="https://www.python.org/downloads/">https://www.python.org/downloads/</a></li>
</ul></li>
<li>Be careful about starting it!
<ul>
<li>You can open it and check the next slide.</li>
</ul></li>
</ul>
</section>
<section id="add-python-to-path" class="level2">
<h2 class="anchored" data-anchor-id="add-python-to-path">Add Python to PATH</h2>
<p><img src="img/add-python-to-path.png" class="img-fluid"></p>
</section>
<section id="why" class="level2">
<h2 class="anchored" data-anchor-id="why">Why?</h2>
<ul>
<li>The benefit of adding Python to path is that we can use it at</li>
<li><dramatic music></li>
<li><em>The Command Line</em>
<ul>
<li>A text-based interface to computing resources, including its ability to do e.g. arithmetic and save notes.</li>
</ul></li>
</ul>
</section>
<section id="terminal" class="level2">
<h2 class="anchored" data-anchor-id="terminal">Terminal</h2>
<ul>
<li>On MS Windows
<ul>
<li>I press Windows key, type “terminal” then press enter.</li>
</ul></li>
<li>On MacOS
<ul>
<li>I open Launchpad, type “terminal” then press enter.</li>
</ul></li>
</ul>
</section>
<section id="macos" class="level2">
<h2 class="anchored" data-anchor-id="macos">MacOS</h2>
<p><img src="img/zsh.avif" class="img-fluid"></p>
</section>
<section id="windows" class="level2">
<h2 class="anchored" data-anchor-id="windows">Windows</h2>
<p><img src="img/ps.webp" class="img-fluid"></p>
</section>
<section id="expression-evaluation" class="level2">
<h2 class="anchored" data-anchor-id="expression-evaluation">Expression evaluation</h2>
<ul>
<li>Returning to the terminal, we can type at the “prompt”.</li>
<li>On MacOS, perhaps a line that begins with <code>$</code> and a flashing cursor</li>
<li>On Window, perhaps <code>PS C:\Users\calvin></code>
<ul>
<li><code>PS</code> stands for “powershell” - more latter.</li>
<li><code>C:\Users\calvin</code> is the name of a folder - more latter</li>
<li><code>></code> is the prompt, with a flashing cursor.</li>
</ul></li>
</ul>
</section>
<section id="run-python" class="level2">
<h2 class="anchored" data-anchor-id="run-python">“Run” Python</h2>
<p><em>In the following examples, I remove line numbers to denote they are not Python code snippets.</em></p>
<ul>
<li>On Windows, type <code>python</code></li>
</ul>
<div class="code-with-filename">
<div class="code-with-filename-file">
<pre><strong>Windows</strong></pre>
</div>
<div class="sourceCode" id="cb1" data-filename="Windows"><pre class="sourceCode ps code-with-copy"><code class="sourceCode postscript"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a>PS C:\Users\calvin> python</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
</div>
<ul>
<li>On MacOS, type <code>python3</code></li>
</ul>
<div class="code-with-filename">
<div class="code-with-filename-file">
<pre><strong>MacOS</strong></pre>
</div>
<div class="sourceCode" id="cb2" data-filename="MacOS"><pre class="sourceCode zsh code-with-copy"><code class="sourceCode zsh"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="ex">$</span> python3</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
</div>
<ul>
<li>On both, press the <strong>↵ᴇɴᴛᴇʀ</strong> key.</li>
</ul>
</section>
<section id="see-python" class="level2">
<h2 class="anchored" data-anchor-id="see-python">See Python</h2>
<ul>
<li>You’ll see something like this:</li>
</ul>
<div class="sourceCode" id="cb3"><pre class="sourceCode email code-with-copy"><code class="sourceCode email"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a>Python 3.12.5 (tags/v3.12.5:ff3bc82, Aug 6 2024, 20:45:27) [MSC v.1940 64 bit (AMD64)] on win32</span>
<span id="cb3-2"><a href="#cb3-2" aria-hidden="true" tabindex="-1"></a>Type "help", "copyright", "credits" or "license" for more information.</span>
<span id="cb3-3"><a href="#cb3-3" aria-hidden="true" tabindex="-1"></a>>>></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<ul>
<li>Take note of the prompt!</li>
<li><code>>>></code></li>
<li>Those three are how you know it is Python, and not the Terminal, that you are working in.</li>
</ul>
</section>
<section id="example" class="level2">
<h2 class="anchored" data-anchor-id="example">Example</h2>
<ul>
<li>If I type <code>python</code> at the command line</li>
<li>Then <code>9 * -1 * -1 + 5</code> <em>within</em> Python</li>
<li>It will look like this:</li>
</ul>
<div class="sourceCode" id="cb4"><pre class="sourceCode email code-with-copy"><code class="sourceCode email"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a>PS C:\Users\calvin> python</span>
<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a>Python 3.12.5 (tags/v3.12.5:ff3bc82, Aug 6 2024, 20:45:27) [MSC v.1940 64 bit (AMD64)] on win32</span>
<span id="cb4-3"><a href="#cb4-3" aria-hidden="true" tabindex="-1"></a>Type "help", "copyright", "credits" or "license" for more information.</span>
<span id="cb4-4"><a href="#cb4-4" aria-hidden="true" tabindex="-1"></a>>>> 9 * -1 * -1 + 5</span>
<span id="cb4-5"><a href="#cb4-5" aria-hidden="true" tabindex="-1"></a>14</span>
<span id="cb4-6"><a href="#cb4-6" aria-hidden="true" tabindex="-1"></a>>>></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<ul>
<li>This is how Python shows that <code>9 * -1 * -1 + 5</code> is <code>14</code></li>
</ul>
</section>
</section>
<section id="why-python" class="level1">
<h1>Why Python?</h1>
<section id="on-python" class="level2">
<h2 class="anchored" data-anchor-id="on-python">On Python</h2>
<ul>
<li>Python is free,</li>
<li>Python is very widely used,</li>
<li>Python is flexible,</li>
<li>Python is relatively easy to learn,</li>
<li>and Python is quite powerful.</li>
</ul>
</section>
<section id="why-not-python" class="level2">
<h2 class="anchored" data-anchor-id="why-not-python">Why not Python?</h2>
<ul>
<li>Python is a general purpose language used for Scientific Computing.</li>
<li><em>Not</em> to build apps, build software, manage databases, or develop user interfaces.</li>
<li>Solve scientific and mathematical problems.</li>
</ul>
</section>
<section id="python-libraries" class="level2">
<h2 class="anchored" data-anchor-id="python-libraries">Python libraries</h2>
<p>Scientists often use the following:</p>
<ul>
<li><a href="https://www.python.org/">Python</a>,</li>
<li><a href="https://www.numpy.org/"><code>numpy</code> (numerical Python)</a>,</li>
<li><a href="https://matplotlib.org/"><code>matplotlib</code> (a suite of plotting tools)</a>,</li>
<li><a href="https://www.scipy.org/"><code>scipy</code> (scientific Python)</a>, and</li>
<li><a href="https://www.sympy.org/en/index.html"><code>sympy</code> (symbolic Python)</a>.</li>
</ul>
<p>We’ll get to these.</p>
</section>
</section>
<section id="running-example" class="level1">
<h1>Running Example</h1>
<section id="diving-in" class="level2">
<h2 class="anchored" data-anchor-id="diving-in">Diving In</h2>
<ul>
<li>Taking Python as a given, we’ll:
<ul>
<li>Use an example of something I helped a student with recently</li>
<li>Show step-by-step how to use Python</li>
<li>Introduce a number of Python features to solve the problem more easily.</li>
</ul></li>
<li>This was from an introductory physics class I believe; I don’t know the context.</li>
</ul>
</section>
<section id="motivating-example" class="level2">
<h2 class="anchored" data-anchor-id="motivating-example">Motivating Example</h2>
<ul>
<li>Recently, I helped a student stuck on this:</li>
</ul>
<p><span class="math display">\[
f(x) =
\begin{cases}
9x^2 + 5 & x < 4 \\
9 & 4 \leq x \leq 8 \\
2 - x & x > 8
\end{cases}
\]</span></p>
<ul>
<li>Find <span class="math inline">\(f(x)\)</span> for each of the following <span class="math inline">\(x\)</span> values: <span class="math display">\[
\{-1, 4, 5, 8, 11\}
\]</span></li>
</ul>
</section>
<section id="is-this-real" class="level2">
<h2 class="anchored" data-anchor-id="is-this-real">Is this “real”?</h2>
<ul>
<li>Models income tax brackets, one of the most important drivers of human behavior in the largest economies in the world.</li>
<li>We use a simpler contrived example for now…</li>
</ul>
<table style="font-size:12px">
<tbody><tr><th>
Marginal Tax Rate
</th>
<th>
Single Taxable Income
</th>
<th>
Married Filing Jointly or Qualified Widow(er) Taxable Income
</th>
<th>
Married Filing Separately Taxable Income
</th>
<th>
Head of Household Taxable Income
</th>
</tr>
<tr>
<th>
10%
</th>
<td>
$0 – $9,275
</td>
<td>
$0 – $18,550
</td>
<td>
$0 – $9,275
</td>
<td>
$0 – $13,250
</td>
</tr>
<tr>
<th>
15%
</th>
<td>
$9,276 – $37,650
</td>
<td>
$18,551 – $75,300
</td>
<td>
$9,276 – $37,650
</td>
<td>
$13,251 – $50,400
</td>
</tr>
<tr>
<th>
25%
</th>
<td>
$37,651 – $91,150
</td>
<td>
$75,301 – $151,900
</td>
<td>
$37,651 – $75,950
</td>
<td>
$50,401 – $130,150
</td>
</tr>
<tr>
<th>
28%
</th>
<td>
$91,151 – $190,150
</td>
<td>
$151,901 – $231,450
</td>
<td>
$75,951 – $115,725
</td>
<td>
$130,151 – $210,800
</td>
</tr>
<tr>
<th>
33%
</th>
<td>
$190,151 – $413,350
</td>
<td>
$231,451 – $413,350
</td>
<td>
$115,726 – $206,675
</td>
<td>
$210,801 – $413,350
</td>
</tr>
<tr>
<th>
35%
</th>
<td>
$413,351 – $415,050
</td>
<td>
$413,351 – $466,950
</td>
<td>
$206,676 – $233,475
</td>
<td>
$413,351 – $441,000
</td>
</tr>
<tr>
<th>
39.6%
</th>
<td>
$415,051+
</td>
<td>
$466,951+
</td>
<td>
$233,476+
</td>
<td>
$441,001+
</td>
</tr></tbody></table>
</section>
<section id="how-to-solve" class="level2">
<h2 class="anchored" data-anchor-id="how-to-solve">How to solve?</h2>
<ul>
<li>Think about how you would solve such a problem.</li>
<li>What steps would you take?</li>
<li>What would making solving it hard?
<ul>
<li>Keep track of details?</li>
<li>Performing the arithmetic?</li>
<li>Anything else?</li>
</ul></li>
<li>Python, in my view, is a way to solve these problems.</li>
</ul>
</section>
<section id="python-in-action" class="level2">
<h2 class="anchored" data-anchor-id="python-in-action">Python in action</h2>
<ul>
<li>My preferred way to do calculation as an experienced Python user is writing <em>code</em>:</li>
</ul>
<div class="columns">
<div class="column" style="width:50%;">
<ul>
<li>Mathematical expression <span class="math display">\[
\begin{cases}
9x^2 + 5 & x < 4 \\
9 & 4 \leq x \leq 8 \\
2 - x & x > 8
\end{cases}
\]</span></li>
</ul>
</div><div class="column" style="width:50%;">
<ul>
<li>Python expression (code)</li>
</ul>
<div id="36bdfd68" class="cell" data-execution_count="2">
<div class="sourceCode cell-code" id="cb5"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb5-1"><a href="#cb5-1"></a><span class="dv">9</span> <span class="op">*</span> <span class="op">-</span><span class="dv">1</span> <span class="op">*</span> <span class="op">-</span><span class="dv">1</span> <span class="op">+</span> <span class="dv">5</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="68">
<pre><code>14</code></pre>
</div>
</div>
</div>
</div>
<ul>
<li>I write <code>x * x</code> for <span class="math inline">\(x^2\)</span> because it’s non-obvious how to write “squared” yet.</li>
</ul>
</section>
<section id="arithmetic-operations" class="level2">
<h2 class="anchored" data-anchor-id="arithmetic-operations">Arithmetic Operations</h2>
<ul>
<li>In Python, we can write many of the same arithmetic operations we use in our math and science classes.</li>
</ul>
<div id="2fc7b017" class="cell" data-execution_count="3">
<div class="sourceCode cell-code" id="cb7"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb7-1"><a href="#cb7-1"></a><span class="dv">6</span> <span class="op">+</span> <span class="dv">3</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="69">
<pre><code>9</code></pre>
</div>
</div>
<div id="d147ffbf" class="cell" data-execution_count="4">
<div class="sourceCode cell-code" id="cb9"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb9-1"><a href="#cb9-1"></a><span class="dv">6</span> <span class="op">-</span> <span class="dv">3</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="70">
<pre><code>3</code></pre>
</div>
</div>
<div id="665f51b1" class="cell" data-execution_count="5">
<div class="sourceCode cell-code" id="cb11"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb11-1"><a href="#cb11-1"></a><span class="dv">6</span> <span class="op">*</span> <span class="dv">3</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="71">
<pre><code>18</code></pre>
</div>
</div>
<div id="927ab745" class="cell" data-execution_count="6">
<div class="sourceCode cell-code" id="cb13"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb13-1"><a href="#cb13-1"></a><span class="dv">6</span> <span class="op">/</span> <span class="dv">3</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="72">
<pre><code>2.0</code></pre>
</div>
</div>
</section>
</section>
<section id="evaluating-expressions" class="level1">
<h1>Evaluating Expressions</h1>
<section id="recall" class="level2">
<h2 class="anchored" data-anchor-id="recall">Recall</h2>
<div class="columns">
<div class="column" style="width:50%;">
<p><span class="math display">\[
\begin{cases}
9x^2 + 5 & x < 4 \\
9 & 4 \leq x \leq 8 \\
2 - x & x > 8
\end{cases}
\]</span> <span class="math display">\[
\{-1, 4, 5, 8, 11\}
\]</span></p>
</div><div class="column" style="width:50%;">
<div class="sourceCode" id="cb15"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb15-1"><a href="#cb15-1" aria-hidden="true" tabindex="-1"></a><span class="op">>>></span> <span class="dv">9</span> <span class="op">*</span> <span class="op">-</span><span class="dv">1</span> <span class="op">*</span> <span class="op">-</span><span class="dv">1</span> <span class="op">+</span> <span class="dv">5</span></span>
<span id="cb15-2"><a href="#cb15-2" aria-hidden="true" tabindex="-1"></a><span class="dv">14</span></span>
<span id="cb15-3"><a href="#cb15-3" aria-hidden="true" tabindex="-1"></a><span class="op">>>></span> <span class="dv">9</span></span>
<span id="cb15-4"><a href="#cb15-4" aria-hidden="true" tabindex="-1"></a><span class="dv">9</span></span>
<span id="cb15-5"><a href="#cb15-5" aria-hidden="true" tabindex="-1"></a><span class="op">>>></span> <span class="dv">9</span></span>
<span id="cb15-6"><a href="#cb15-6" aria-hidden="true" tabindex="-1"></a><span class="dv">9</span></span>
<span id="cb15-7"><a href="#cb15-7" aria-hidden="true" tabindex="-1"></a><span class="op">>>></span> <span class="dv">9</span></span>
<span id="cb15-8"><a href="#cb15-8" aria-hidden="true" tabindex="-1"></a><span class="dv">9</span></span>
<span id="cb15-9"><a href="#cb15-9" aria-hidden="true" tabindex="-1"></a><span class="op">>>></span> <span class="dv">2</span> <span class="op">-</span> <span class="dv">11</span></span>
<span id="cb15-10"><a href="#cb15-10" aria-hidden="true" tabindex="-1"></a><span class="op">-</span><span class="dv">9</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
</div>
</div>
<ul>
<li>This is still quite tedious and annoying!</li>
</ul>
</section>
<section id="inequality-testing" class="level2">
<h2 class="anchored" data-anchor-id="inequality-testing">(In)equality testing</h2>
<ul>
<li>Like <code>+</code> or <code>-</code> which we use to calculate numbers…</li>
<li>We can use <code><</code> or <code>></code> to calculate inequalities.</li>
<li>Specifically, we see whether an inequality is <code>True</code> or <code>False</code></li>
</ul>
<div id="6455f382" class="cell" data-execution_count="7">
<div class="sourceCode cell-code" id="cb16"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb16-1"><a href="#cb16-1"></a><span class="op">-</span><span class="dv">1</span> <span class="op"><</span> <span class="dv">4</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="73">
<pre><code>True</code></pre>
</div>
</div>
<div id="68e5d5a1" class="cell" data-execution_count="8">
<div class="sourceCode cell-code" id="cb18"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb18-1"><a href="#cb18-1"></a><span class="dv">4</span> <span class="op"><</span> <span class="dv">4</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="74">
<pre><code>False</code></pre>
</div>
</div>
</section>
<section id="accomodating-keyboards" class="level2">
<h2 class="anchored" data-anchor-id="accomodating-keyboards">Accomodating Keyboards</h2>
<ul>
<li>Some things aren’t super easy to type.</li>
<li>I don’t have a “<span class="math inline">\(\leq\)</span>” key on my keyboard.</li>
<li>Combine with <code>=</code> as <code><=</code> for “less than or equal” or “<span class="math inline">\(\leq\)</span>”</li>
</ul>
<div id="034b28af" class="cell" data-execution_count="9">
<div class="sourceCode cell-code" id="cb20"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb20-1"><a href="#cb20-1"></a><span class="dv">4</span> <span class="op"><=</span> <span class="dv">4</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="75">
<pre><code>True</code></pre>
</div>
</div>
<ul>
<li>We can “chain” inequalities as well - one after another.</li>
</ul>
<div id="32b76253" class="cell" data-execution_count="10">
<div class="sourceCode cell-code" id="cb22"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb22-1"><a href="#cb22-1"></a><span class="dv">4</span> <span class="op"><=</span> <span class="dv">4</span> <span class="op"><=</span> <span class="dv">8</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="76">
<pre><code>True</code></pre>
</div>
</div>
</section>
<section id="a-note" class="level2">
<h2 class="anchored" data-anchor-id="a-note">A note</h2>
<ul>
<li>We always put the equal sign <code>=</code> second.</li>
</ul>
<div id="45a611f6" class="cell" data-execution_count="11">
<div class="sourceCode cell-code" id="cb24"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb24-1"><a href="#cb24-1"></a><span class="dv">4</span> <span class="op"><=</span> <span class="dv">5</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="77">
<pre><code>True</code></pre>
</div>
</div>
<div id="bf2938e0" class="cell" data-execution_count="12">
<div class="sourceCode cell-code" id="cb26"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb26-1"><a href="#cb26-1"></a><span class="dv">5</span> <span class="op">>=</span> <span class="dv">4</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="78">
<pre><code>True</code></pre>
</div>
</div>
<ul>
<li>A (somewhat confusing) error if we try <code>=></code></li>
</ul>
<div class="sourceCode" id="cb28"><pre class="sourceCode email code-with-copy"><code class="sourceCode email"><span id="cb28-1"><a href="#cb28-1" aria-hidden="true" tabindex="-1"></a>>>> 4 => 5</span>
<span id="cb28-2"><a href="#cb28-2" aria-hidden="true" tabindex="-1"></a> File "<stdin>", line 1</span>
<span id="cb28-3"><a href="#cb28-3" aria-hidden="true" tabindex="-1"></a> 4 => 5</span>
<span id="cb28-4"><a href="#cb28-4" aria-hidden="true" tabindex="-1"></a> ^</span>
<span id="cb28-5"><a href="#cb28-5" aria-hidden="true" tabindex="-1"></a><span class="fu">SyntaxError: </span>cannot assign to literal</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
</section>
</section>
<section id="and" class="level1">
<h1><code>=</code> and <code>==</code></h1>
<section id="new-topics" class="level2">
<h2 class="anchored" data-anchor-id="new-topics">New Topics</h2>
<ul>
<li>We have now touch on two new topics:
<ul>
<li><code>True</code> and <code>False</code>
<ul>
<li>Expressions which don’t <em>evaluate</em> to a number</li>
<li>Called “booleans”</li>
</ul></li>
<li>“Assignment”
<ul>
<li>Associated with the <code>=</code> sign</li>
<li>Different from inequality testing!</li>
</ul></li>
</ul></li>
<li>We’ll explore both!</li>
</ul>
</section>
<section id="booleans" class="level2">
<h2 class="anchored" data-anchor-id="booleans">Booleans</h2>
<ul>
<li>Sometimes, a Python <em>expression</em> is a numerical value.</li>
</ul>
<div id="168d1cb6" class="cell" data-execution_count="13">
<div class="sourceCode cell-code" id="cb29"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb29-1"><a href="#cb29-1"></a><span class="dv">2</span> <span class="op">+</span> <span class="dv">2</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="79">
<pre><code>4</code></pre>
</div>
</div>
<div id="ae10d3d6" class="cell" data-execution_count="14">
<div class="sourceCode cell-code" id="cb31"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb31-1"><a href="#cb31-1"></a><span class="dv">7</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="80">
<pre><code>7</code></pre>
</div>
</div>
<ul>
<li>But it doesn’t have to be!</li>
</ul>
<div id="af7ee5fc" class="cell" data-execution_count="15">
<div class="sourceCode cell-code" id="cb33"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb33-1"><a href="#cb33-1"></a><span class="dv">2</span> <span class="op"><</span> <span class="dv">2</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display" data-execution_count="81">
<pre><code>False</code></pre>
</div>
</div>
</section>
<section id="if" class="level2">
<h2 class="anchored" data-anchor-id="if">If</h2>
<ul>
<li>Booleans are mostly useful for writing <code>if</code> statements.
<ul>
<li>These are <em>multiline</em> expressions in Python.</li>
</ul></li>
<li>To see the result of multi-line expression, we have to print the result…</li>
</ul>
<div id="9cda29f7" class="cell" data-execution_count="16">
<div class="sourceCode cell-code" id="cb35"><pre class="sourceCode numberSource python number-lines code-with-copy"><code class="sourceCode python"><span id="cb35-1"><a href="#cb35-1"></a><span class="cf">if</span> (<span class="dv">1</span> <span class="op"><=</span> <span class="dv">1</span>):</span>
<span id="cb35-2"><a href="#cb35-2"></a> <span class="bu">print</span>(<span class="dv">2</span> <span class="op">+</span> <span class="dv">2</span>)</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-stdout">
<pre><code>4</code></pre>
</div>
</div>
<div id="b2550288" class="cell" data-execution_count="17">