Variable reuse is something we see in big chunks of code.
TL;DR: Don't reuse variable names. You break readability and refactor chances and gain nothing but laziness.
Problems
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Readability
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Refactor chances
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Missed Optimization
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Mutability
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Garbage Collection Missed Opportunities
Solutions
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Define, use and dispose variables.
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Keep your Definition, Usage and Destroy variables short.
Sample Code
Wrong
class Item: def __init__(self, name): self.name = name def taxesCharged(self): return 1; class Money: pass lastPurchase = Item('Soda'); # Do something with the purchase taxAmount = lastPurchase.taxesCharged(); # Lots of stuff related to the purchase # I drink the soda # I cannot extract method from below without passing # useless lastPurchase as parameter # a few hours later.. lastPurchase = Item('Whisky'); # I bough another drink taxAmount += lastPurchase.taxesCharged(); Right
class Item: def __init__(self, name): self.name = name def taxesCharged(self): return 1; class Money: pass def buySupper(): supperPurchase = Item('Soda'); # Do something with the purchase # Lots of stuff related to the purchase # I drink the soda return supperPurchase; def buyDrinks(): # I could extract method! # a few hours later.. drinksPurchase = Item('Whisky'); # I bough another drink return drinksPurchase; taxAmount = buySupper().taxesCharged() + buyDrinks().taxesCharged(); Detection
Many linters can warn us from reusing variables
Tags
- Readability
Conclusion
Reusing variables is a non-contextual copy and paste hint.
Relations
More Info
Credits
Photo by Robby McCullough on Unsplash
Either way you look at it (DRY or laziness), the idea is the same: make your program flexible. When change comes (and it always does), you'll have a much easier time changing with it.
Chris Pine
This article is part of the CodeSmell Series.
Last update: 2021/07/14