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<div class="section" id="style-and-naming">
<span id="id1"></span><h1>Style and Naming<a class="headerlink" href="#style-and-naming" title="Permalink to this headline"></a></h1>
<p class="centered">
<strong><strong>Style matters!</strong></strong></p><div class="section" id="pep-8-reminder">
<h2>PEP 8 reminder<a class="headerlink" href="#pep-8-reminder" title="Permalink to this headline"></a></h2>
<p>PEP 8 (Python Enhancement Proposal 8):</p>
<p><a class="reference external" href="https://www.python.org/dev/peps/pep-0008/">https://www.python.org/dev/peps/pep-0008/</a></p>
<p>Is the “official” style guide for Python code.</p>
<p>Strictly speaking, you only need to follow it for code in the standard library.</p>
<p>But style matters – consistent style makes your code easier to read and understand.</p>
<p>And everyone in the community has accepted PEP 8 as <em>the</em> Python style guide.</p>
<p>So <strong>follow PEP 8</strong></p>
<p><strong>Exception:</strong> if you have a company style guide – follow that instead.</p>
<p>Try the “pycodestyle” module on your code:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ python3 -m pip install pycodestyle
$ pycodestyle my_python_file
</pre></div>
</div>
<p>Try it now – really!</p>
<p>Note that ideally you have a linter installed in your editor that yells at you if you violate PEP8 – no need to run <code class="docutils literal notranslate"><span class="pre">pycodestyle</span></code> if it’s already in your editor.</p>
<p>See: <a class="reference internal" href="../topics/01-setting_up/python_and_core_tools.html#editor-for-python"><span class="std std-ref">Text Editors Only</span></a> for suggestions on editors and configuration.</p>
</div>
<div class="section" id="naming-things">
<h2>Naming Things…<a class="headerlink" href="#naming-things" title="Permalink to this headline"></a></h2>
<p>It matters what names you give your variables.</p>
<p>Python has rules about what it <em>allows</em>.</p>
<p>PEP 8 has rules for style: capitalization, and underscores and all that.</p>
<p>But you still get to decide within those rules.</p>
<p>So use names that make sense to the reader.</p>
<div class="section" id="naming-guidelines">
<h3>Naming Guidelines<a class="headerlink" href="#naming-guidelines" title="Permalink to this headline"></a></h3>
<p>Whenever possible, use strong, unambiguous names that relate to a concept in the business area applicable for your program.
For example, <code class="docutils literal notranslate"><span class="pre">cargo_weight</span></code> is probably better than <code class="docutils literal notranslate"><span class="pre">item_weight</span></code>, <code class="docutils literal notranslate"><span class="pre">current_fund_price</span></code> is better than <code class="docutils literal notranslate"><span class="pre">value</span></code>. But all of those are better than <code class="docutils literal notranslate"><span class="pre">item</span></code>, or <code class="docutils literal notranslate"><span class="pre">x</span></code>, or …</p>
<p>Only use single-letter names for things with limited scope: indexes and the like:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="k">for</span> <span class="n">i</span><span class="p">,</span> <span class="n">item</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">(</span><span class="n">a_sequence</span><span class="p">):</span>
<span class="n">do_something</span><span class="p">(</span><span class="n">i</span><span class="p">,</span> <span class="n">item</span><span class="p">)</span>
</pre></div>
</div>
<p>But <strong>don’t</strong> use a name like “item”, when there is a meaning to what the item is:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="k">for</span> <span class="n">name</span> <span class="ow">in</span> <span class="n">all_the_names</span><span class="p">:</span>
<span class="n">do_something_with</span><span class="p">(</span><span class="n">name</span><span class="p">)</span>
</pre></div>
</div>
<p>Use plurals for collections of things:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="n">names</span> <span class="o">=</span> <span class="p">[</span><span class="s1">'Fred'</span><span class="p">,</span> <span class="s1">'George'</span><span class="p">,</span> <span class="o">...</span><span class="p">]</span>
</pre></div>
</div>
<p>And then singular for a single item in that collection:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="k">for</span> <span class="n">name</span> <span class="ow">in</span> <span class="n">names</span><span class="p">:</span>
<span class="o">...</span>
</pre></div>
</div>
<p><strong>Do</strong> re-use names when the use is essentially the same, and you don’t need the old one:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="n">line</span> <span class="o">=</span> <span class="n">line</span><span class="o">.</span><span class="n">strip</span><span class="p">()</span>
<span class="n">line</span> <span class="o">=</span> <span class="n">line</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="s2">","</span><span class="p">,</span> <span class="s2">" "</span><span class="p">)</span>
<span class="o">....</span>
</pre></div>
</div>
</div>
<div class="section" id="what-about-hungarian-notation">
<h3>What about Hungarian Notation?<a class="headerlink" href="#what-about-hungarian-notation" title="Permalink to this headline"></a></h3>
<p><a class="reference external" href="https://en.wikipedia.org/wiki/Hungarian_notation">Hungarian Notation</a>
is a naming system where the data type is part of the name:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="n">strFirstName</span> <span class="o">=</span> <span class="s2">"Chris"</span>
<span class="n">listDonations</span> <span class="o">=</span> <span class="p">[</span><span class="mf">400.0</span><span class="p">,</span> <span class="mf">125.0</span><span class="p">,</span> <span class="mf">1000.0</span><span class="p">]</span>
<span class="n">int_num_days</span> <span class="o">=</span> <span class="mi">30</span>
</pre></div>
</div>
<p>This method is not recommended nor widely used in the Python community.</p>
<p>One reason is Python’s dynamic typing – it really isn’t important what type a value is, but rather, what it means.
And you may end up refactoring the code to use a different type, and then do you want to have to rename everything?
Or worse, the type in the name no longer matches the actual type in the code – and that’s really bad. I have seen code like this:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="n">strNumber</span> <span class="o">=</span> <span class="nb">input</span><span class="p">(</span><span class="s2">"How many would you like?"</span><span class="p">)</span>
<span class="n">strNumber</span> <span class="o">=</span> <span class="nb">int</span><span class="p">(</span><span class="n">strNumber</span><span class="p">)</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">strNumber</span><span class="p">):</span>
<span class="o">...</span>
</pre></div>
</div>
<p>So you have a name used for a string, then it gets converted to an integer, and the data type no longer matches the name. Wouldn’t you be better off if that had never been named with the type in the first place?</p>
<p>While widely used in some circles, it is generally considered bad style in the Python community – so:</p>
<p class="centered">
<strong><strong>Do Not Use Hungarian Notation</strong></strong></p></div>
<div class="section" id="more-about-naming-things">
<h3>More About Naming Things<a class="headerlink" href="#more-about-naming-things" title="Permalink to this headline"></a></h3>
<p>Here’s a nice talk about naming:</p>
<p><a class="reference external" href="https://www.youtube.com/watch?v=hZ7hgYKKnF0">Jack Diederich: Name Things Once</a></p>
<p>One note about that talk – Jack is mostly encouraging people to not use names that are too long and unnecessarily specific.
However, with beginners, it’s often tempting to use names that are too <em>short</em> and <em>non-specific</em>, like “x” and “item” – so you need to strike a balance, but absolutely:</p>
<p class="centered">
<strong><strong>Use Meaningful Names</strong></strong></p></div>
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