Python idiom for iterating over changing list

Question

Is there a better (more obvious/idiomatic) way in python to write an equivalent of

index = 0
while index < len(some_list):
    do_some_stuff(some_list[index])         


        

Answer 1

If order doesn't matter, you can enumerate backwards so that deletes don't mess up the part of the list you haven't processed yet.

for i, item in enumerate(reversed(somelist), -len(somelist)+1):
    do_some_stuff(item)
    if delete_element(item):
        del somelist[-i]

If order does matter, reverse the list, do this trick then reverse it again. That'll confuse 'em!

Depending on the situation, you could replace the item with a marker like None. Either strip it out later or have other places this list is used chack None.

for i, item in enumerate(somelist)):
    do_some_stuff(item)
    if delete_element(item):
        somelist[i] = None

somelist = [item for item in somelist if item]