CODEWITHSUNDEEP
pythonlistelement
Anan
Anan

Reputation: 31

Remove elements from python list

I'm trying to understand the logic here, why this code doesn't remove all elements in the list?

int_lst = [1, 2, 3, 4, 5, 6]

for i in int_lst:
    int_lst.remove(i)
    print(int_lst)

print(int_lst)  #Output: [2, 4, 6]

Upvotes: 0

Views: 113

Answers (2)

Scrap
Scrap

Reputation: 123

That happens because you are removing elements in the same list you are iterating through. You can easily fix it by avoiding this:

for i in list(int_lst):
    int_lst.remove(i)

Upvotes: 0

chepner
chepner

Reputation: 530970

When you remove an element, everything after that element effectively moves back one place. But the iterator doesn't know that: it just advance the pointer to the next element, skipping what should have been the next value bound to i.

In detail, i starts at 1. You remove it, and now 2 is in the current position of the iterator. The iterator advances, and now 3 is in the current position and bound to i.

In other words, every time you remove an element, you effectively advance the iterator, in addition to the explicit advancement the iterator will perform.

Upvotes: 1

Related Questions