Mats Wichmann wrote:
> On 9/7/20 5:01 PM, Driuma Nikita wrote:
>
>
> _list = list(range(50))
> for i, el in enumerate(_list):
> del _list[i]
> print(_list)
>
>
> Don't change the the list while you are iterating over it, it messes up
> the iteration. It's not "randomly deleting", it's when next is called to
> fetch the next item, the list has changed.
>
> One workaround is to iterate over a copy. For example here's using
> slicing to create a new list to iterate over:
>
> for i, el in enumerate(_list[:]):
> del _list[i]
As Richard says, this won't work.
Usually the best approach is to copy the items you want to keep:
_list = [item for item in _list if keep(item)]
If the list is huge you can also delete in reverse order:
for i in reversed(len(_list)):
if discard(_list[i]):
del _list[i]
(If you want to delete /all/ items use _list.clear() or del _list[:])
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