Lambda in a Loop is a Code Smell

Watch out for smelly code!

A common mistake in Python is to use a lambda function inside of a loop. While it's not always a problem, it should set off your senses to take a second look when you see a lambda inside a loop. If the lambda references a loop variable, you might not realize that the way that closures (or cell variables) work in Python means the lambda doesn't store the latest value of a variable that was present when the lambda is created. In this video I walk through a simplified real-world-code example where I made this mistake myself, including how to fix it.


― mCoding with James Murphy (mcoding.io/)

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Closures video:    • Functions within functions, closures, and ...  
Local vs global lookup video:    • Local and Global Variable Lookup Weirdness...  


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CHAPTERS
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0:00 Intro
0:12 What is a code smell?
0:43 Sponsoring myself!
1:11 Example setup
2:49 The symptoms
4:02 Why the lambda in a loop is bad
5:00 The partial fix
5:59 Exceptions to the rule
7:15 Prevent this before it ever happens
8:00 Thank