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<h1>Hunting snakes with a shotgun
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<h4>Python is a little too forgiving
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<p><em>2019-06-27 03:00:00 -0400
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<p>A rather large number of people know me as “the guy who does weird things with python”. I would object to this title, but it is quite accurate. So, here are some of the things I like playing with in python. None of these are actually breaking the language, just little known facts and syntax. At some point I will share about actually breaking the language. For now, enjoy the weird things I have found over the past 6 years.</p>
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<h2 id="type-hints">Type hints</h2>
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<p>A little known feature of python is called “type hinting” (PEP 484). This is actually quite common to see in standard libraries, and has it’s own special syntax:</p>
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<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># Here is a regular function
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</span><span class="k">def</span> <span class="nf">meep</span><span class="p">(</span><span class="n">a</span><span class="p">,</span> <span class="n">b</span><span class="p">):</span>
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<span class="k">return</span> <span class="n">a</span><span class="o">*</span><span class="n">b</span><span class="o">^</span><span class="mi">2</span>
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<span class="c1"># This function has no real reason to exsist, and is lacking any sort of documentation.
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# Let's add a docstring to explain what it does
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</span>
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<span class="k">def</span> <span class="nf">meep</span><span class="p">(</span><span class="n">a</span><span class="p">,</span> <span class="n">b</span><span class="p">):</span>
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<span class="s">""" This function returns the result of a times b squared """</span>
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<span class="k">return</span> <span class="n">a</span><span class="o">*</span><span class="n">b</span><span class="o">^</span><span class="mi">2</span>
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<span class="c1"># Ok. The docstring explains the function, but is not too helpful
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# what are a and b? what does this return?
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# For all we know, a could actually be a string (in which case, this function would return a string)
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# Let's fix that up with a type hint
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</span>
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<span class="k">def</span> <span class="nf">meep</span><span class="p">(</span><span class="n">a</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">b</span><span class="p">:</span> <span class="nb">int</span><span class="p">):</span>
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<span class="s">""" This function returns the result of a times b squared """</span>
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<span class="k">return</span> <span class="n">a</span><span class="o">*</span><span class="n">b</span><span class="o">^</span><span class="mi">2</span>
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<span class="c1"># Thanks to the :int (called a type hint in case you didn't notice that yet), we now know that this function expects two ints.
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# Now, to finish this up with a secondary type hint to specify the return type
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</span><span class="k">def</span> <span class="nf">meep</span><span class="p">(</span><span class="n">a</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">b</span><span class="p">:</span> <span class="nb">int</span><span class="p">)</span> <span class="o">-></span> <span class="nb">int</span><span class="p">:</span>
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<span class="s">""" This function returns the result of a times b squared """</span>
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<span class="k">return</span> <span class="n">a</span><span class="o">*</span><span class="n">b</span><span class="o">^</span><span class="mi">2</span>
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<span class="c1"># There. Now we can clearly see that this function takes too ints, and returns one int.
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# If only this was a requirement in the language. So many headaches could be solved.
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</span></code></pre></div></div>
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<p>Now, keep in mind that this is called a type <em>hint</em>. The python compiler (yes.. Give me a second for that one) does not actually care if you obey the hint or not. Feel free to send incorrect data into a hinted function and see what you can break. Critical functions should both hint and check the data types being provided.</p>
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<h2 id="type-declarations">Type declarations</h2>
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<p>Just like type hints for functions, python has hints for variables too.</p>
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<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># A regular variable. Must be declared with an initial value
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</span><span class="n">my_state</span> <span class="o">=</span> <span class="bp">None</span>
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<span class="c1"># my_state is None, as it has not been set, but needs to exist.
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# Let's assume that my_state is to be a state:
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</span><span class="k">class</span> <span class="nc">State</span><span class="p">:</span>
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<span class="n">status</span> <span class="o">=</span> <span class="bp">False</span>
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<span class="k">def</span> <span class="nf">toggle</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
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<span class="bp">self</span><span class="o">.</span><span class="n">status</span> <span class="o">!=</span> <span class="bp">self</span><span class="o">.</span><span class="n">status</span>
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<span class="c1"># Finally, its time to set the state to something useful
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</span><span class="n">my_state</span> <span class="o">=</span> <span class="n">State</span><span class="p">()</span>
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<span class="n">my_state</span><span class="o">.</span><span class="n">toggle</span><span class="p">()</span>
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<span class="c1"># Ok.. I hate this. Let's start by using type declarations first
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# Any variable can be un-initialized and just have a type. Like so:
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</span><span class="n">my_state</span><span class="p">:</span> <span class="n">State</span>
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<span class="c1"># This works for anything
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</span><span class="n">is_alive</span><span class="p">:</span> <span class="nb">bool</span>
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<span class="n">age</span><span class="p">:</span> <span class="nb">int</span>
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<span class="n">name</span><span class="p">:</span> <span class="nb">str</span>
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<span class="c1"># Now, with this new knowledge, let's rewrite State
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</span><span class="k">class</span> <span class="nc">State</span><span class="p">:</span>
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<span class="n">status</span><span class="p">:</span> <span class="nb">bool</span>
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<span class="k">def</span> <span class="nf">toggle</span><span class="p">(</span><span class="bp">self</span><span class="p">:</span> <span class="n">State</span><span class="p">)</span> <span class="o">-></span> <span class="bp">None</span><span class="p">:</span>
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<span class="bp">self</span><span class="o">.</span><span class="n">status</span> <span class="o">!=</span> <span class="bp">self</span><span class="o">.</span><span class="n">status</span>
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<span class="c1"># And initialize my_state with slightly different syntax
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</span><span class="n">my_state</span> <span class="o">=</span> <span class="n">State</span><span class="p">(</span><span class="n">status</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
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</code></pre></div></div>
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<p>I have not found much use for this yet. Hopefully there is something cool to use it for.</p>
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<h2 id="one-line-functions">One-line functions</h2>
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<p>This is more common knowlage. A function can be declared in one line</p>
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<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># Here is an adder function
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</span><span class="k">def</span> <span class="nf">adder1</span><span class="p">(</span><span class="n">a</span><span class="p">:</span><span class="nb">int</span><span class="p">,</span> <span class="n">b</span><span class="p">:</span><span class="nb">int</span><span class="p">)</span> <span class="o">-></span> <span class="nb">int</span><span class="p">:</span>
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<span class="k">return</span> <span class="n">a</span><span class="o">+</span><span class="n">b</span>
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<span class="c1"># Here is a one-line adder function
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</span><span class="n">adder2</span> <span class="o">=</span> <span class="k">lambda</span> <span class="n">a</span><span class="p">,</span><span class="n">b</span> <span class="p">:</span> <span class="n">a</span><span class="o">+</span><span class="n">b</span>
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<span class="c1"># State from above can be compacted further:
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</span><span class="k">class</span> <span class="nc">State</span><span class="p">:</span>
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<span class="n">status</span><span class="p">:</span> <span class="nb">bool</span>
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<span class="n">toggle</span> <span class="o">=</span> <span class="k">lambda</span> <span class="bp">self</span><span class="p">:</span> <span class="bp">self</span><span class="o">.</span><span class="n">status</span> <span class="o">!=</span> <span class="bp">self</span><span class="o">.</span><span class="n">status</span>
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</code></pre></div></div>
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<h2 id="ternary-operations">Ternary operations</h2>
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<p>On the trend of one-line code, We have the one-line if/else, also known as a Ternary in more sensible languages.</p>
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<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># Here is an if/else
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</span><span class="k">if</span> <span class="mi">100</span> <span class="ow">is</span> <span class="mi">5</span><span class="p">:</span>
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<span class="k">print</span><span class="p">(</span><span class="s">"The world has ended"</span><span class="p">)</span>
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<span class="k">else</span><span class="p">:</span>
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<span class="k">print</span><span class="p">(</span><span class="s">"All is good"</span><span class="p">)</span>
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<span class="c1"># Here is a smaller if/else
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</span><span class="k">print</span><span class="p">(</span><span class="s">"The world has ended"</span> <span class="k">if</span> <span class="mi">100</span> <span class="ow">is</span> <span class="mi">5</span> <span class="k">else</span> <span class="s">"All is good"</span><span class="p">)</span>
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</code></pre></div></div>
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<h2 id="compiled-python">Compiled python</h2>
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<p>This one is interesting. Python, like Java, is compiled into bytecode. So yes, it technically is a compiled language. To see said bytecode, take a look at any <code class="highlighter-rouge">.pyc</code> file sitting in your <code class="highlighter-rouge">__pycache__</code></p>
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<h2 id="blog-formatting-experiments">Blog formatting experiments</h2>
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<p>I am still playing with post formats, and various types of content. This is more random than I usually prefer. Let me know your thoughts on the social media platform of your choosing.</p>
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Site design by: <a href="https://retrylife.ca">Evan Pratten</a> |
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This site was last updated at: 2019-11-30 11:30:39 -0500
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