[Tut] Python Ternary — Tuple Syntax Hack

[Tut] Python Ternary — Tuple Syntax Hack - Printable Version

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[Tut] Python Ternary — Tuple Syntax Hack - xSicKxBot - 07-12-2020

Python Ternary — Tuple Syntax Hack

<div>You may know the ternary operator <code>x if c else y</code> in Python which reads as “return <code>x</code> if <code>c</code> else return <code>y</code>“. But you may not know that you can also write the ternary operator in a shorter form as <code>(y, x)[c]</code>. Let’s dive into this concise way of hacking your own ternary operator!
<figure class="wp-block-image size-large is-resized"><img src="https://blog.finxter.com/wp-content/uploads/2020/07/tuple-1024x576.jpg" alt="Python Ternary Tuple Syntax" class="wp-image-10701" width="768" height="432" srcset="https://blog.finxter.com/wp-content/uploads/2020/07/tuple-scaled.jpg 1024w, https://blog.finxter.com/wp-content/uploads/2020/07/tuple-300x169.jpg 300w, https://blog.finxter.com/wp-content/uploads/2020/07/tuple-768x432.jpg 768w" sizes="(max-width: 768px) 100vw, 768px" /></figure>
A shorthand form of the <a href="https://blog.finxter.com/python-one-line-ternary/" target="_blank" rel="noreferrer noopener" title="Python One Line Ternary">ternary operator</a> is the following tuple syntax hack.
Syntax: You can use the <a href="https://blog.finxter.com/python-tuple-to-integer/" target="_blank" rel="noreferrer noopener" title="Python Tuple to Integer">tuple </a>syntax <code>(x, y)[c]</code> consisting of a tuple <code>(x, y)</code> and a condition <code>c</code> enclosed in a square bracket. Here’s a more intuitive way to represent this tuple syntax.
<pre class="wp-block-preformatted">(<OnFalse>, <OnTrue>)[<Condition>]</pre>
<figure class="wp-block-table is-style-stripes">
<table>
<thead>
<tr>
<th>Operand</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr>
<td><OnTrue></td>
<td>The return expression of the operator in case the condition evaluates to <code>True</code></td>
</tr>
<tr>
<td><Condition></td>
<td>The condition that determines whether to return the <On True> or the <On False> branch.</td>
</tr>
<tr>
<td><OnFalse></td>
<td>The return expression of the operator in case the condition evaluates to <code>False</code></td>
</tr>
</tbody>
</table><figcaption>Tuple Syntax of the Ternary Operator</figcaption></figure>
 <iframe src="https://trinket.io/embed/python/8b1118a41c" width="100%" height="500" frameborder="0" marginwidth="0" marginheight="0" allowfullscreen></iframe> 
Exercise: Run the code and compare both ternary operators—the original and the tuple syntax hack. 
In fact, the order of the <code><OnFalse></code> and <code><OnTrue></code> operands is just flipped when compared to the <a href="https://blog.finxter.com/if-then-else-in-one-line-python/" target="_blank" rel="noreferrer noopener" title="https://blog.finxter.com/if-then-else-in-one-line-python/">basic ternary operator</a>. First, you have the branch that’s returned if the condition does NOT hold. Second, you run the branch that’s returned if the condition holds.
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">age = 17
print(('wtf', 'What?')[age<20]) 'What?'</pre>
The condition <code>age<20</code> holds so the return value passed into the <code><a href="https://blog.finxter.com/the-separator-and-end-arguments-of-the-python-print-function/" title="Python Print Function [And Its SECRET Separator & End Arguments]">print()</a></code> function is the <code><OnTrue></code> branch <code>'What?'</code>. Don’t worry if this confuses you—you’re not alone. Let’s clarify why this tuple syntax works the way it does!
First, you create a tuple <code>('wtf', 'What?')</code>. To access the first tuple value <code>'wtf'</code>, you’d use the standard <a href="https://blog.finxter.com/introduction-to-slicing-in-python/" target="_blank" rel="noreferrer noopener" title="Introduction to Slicing in Python">indexing syntax</a> <code>('wtf', 'What?')[0]</code>. To access the second tuple value <code>'What?'</code>, you’d use the standard indexing syntax <code>('wtf', 'What?')[1]</code>.
Second, you create a condition <code>age<20</code>. You use this condition as the indexing value. You end up with either <code>('wtf', 'What?')[False]</code> or <code>('wtf', 'What?')[True]</code>. As you may know, the Booleans <code>False</code> and <code>True</code> are represented through integers <code>0</code> and <code>1</code> in <a href="https://blog.finxter.com/python-crash-course/" target="_blank" rel="noreferrer noopener" title="Python Programming Tutorial [+Cheat Sheets]">Python</a>. Thus, you get <code>('wtf', 'What?')[0]</code> and <code>('wtf', 'What?')[1]</code>, respectively.
In other words: if your condition evaluates to <code>False</code>, you access the first tuple value. If your condition evaluates to <code>True</code>, you access the second tuple value. 
<h2>Where to Go From Here?</h2>
Enough theory, let’s get some practice!
To become successful in coding, you need to get out there and solve real problems for real people. That’s how you can become a six-figure earner easily. And that’s how you polish the skills you really need in practice. After all, what’s the use of learning theory that nobody ever needs?
Practice projects is how you sharpen your saw in coding!
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Then become a Python freelance developer! It’s the best way of approaching the task of improving your Python skills—even if you are a complete beginner.
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</div>

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