Mistake in List Iteration

This post is taking from Indently’s shorts at https://www.youtube.com/shorts/X8KL7iAk-7k.

List Item Removal

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Suppose we want to remove an item within a list. Such as ‘B’.

And below is one of the common mistakes that junior developer makes. It uses for-loop to remove the item while iterating through the list.

But the result shows an unexpected behavior here. See the code below.

items1 = ['A', 'B', 'C', 'D', 'E']
items2 = []

for item in items1:
    if item == 'B':
        items1.remove('B')
    else:
        items2.append(item)

print(items2)
# ['A', 'D', 'E']

Supposed we are expecting the result to be ['A', 'C', 'D', 'E']. If you want to modify the original list, simply create another list.

And below here is the correct way.

items1 = ['A', 'B', 'C', 'D', 'E']
items2 = [ item for item in items1 if item != 'B' ]
print(items2)
# ['A', 'C', 'D', 'E']

Links

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Indently’s YT video at 10 Nooby Mistakes Devs Often Make In Python: