python - I'm trying to learn why I can't seem to delete every index in a list with a loop -


this question has answer here:

i'm not sure why list not deleting every char indexed based on second list. below code:

l1 = ['e', 'i', 'l', 'n', 's', 't'] l2 = ['e', 'i', 'l', 'n', 's', 't']  n_item in range(len(l1)):     if l1[n_item] in l2:      del l2[n_item]

below error i'm getting:

 traceback (most recent call last):  file "<pyshell#241>", line 3, in <module>  del l2[n_item]  indexerror: list assignment index out of range

thanks ....

as remove earlier items, list becomes shorter, later indicies don't exist. symptom of iterating index in python - terrible idea. it's not how python designed , make unreadable, slow, inflexible code.

instead, use list comprehension construct new list:

[item item in l1 if item not in l2]

note if l2 large, might worth making set first, membership tests on set quicker.


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