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Python Python Collections (Retired) Lists Redux Disemvoweled

Andrew Diodati
Andrew Diodati
3,256 Points

Mutating Lists Over Which We Are Iterating

This question is sort-of above and beyond the topic at hand, but I would like to ask it anyway.

I have been told that it is generally bad practice to mutate a list when you are iterating over it. This is why we often see a "copy" list when we run some loops. Why, then, is it acceptable to use .remove() on state_list (given the code from the video)? Is it because of the embedded for loop - so we are technically not iterating over state_list but rather vowels instead at that exact moment?

Thank you!

1 Answer

Ricky Catron
Ricky Catron
13,023 Points

I would describe it like telling a track runner to run 100 meters then as they run dig a hole at 50 meters. Suddenly boom something they expected was not there. A copy of the list can be used so the loop doesn't hit the hole but you can still remove things as needed.

What I usually do instead is add the items I would have kept to a new list.

Goodluck! --Ricky