Delete list elements after using them

Question

I have a list

test_list = [1,2,3,4,5]

I want to iterate over the elements of this list and delete them after using. But when I try to do this

for element in test_list:
    print element
    test_list.remove(element)

Alternate elements are printed and removed from test_list

1
3
5
print test_list
[2, 4]

Please explain why this happens!

Look at the "Related" list. You will find several duplicates with answers. — mkiever, Sep 02 '15 at 21:31
Repeat after me: Don't modify things while you're iterating over them. — Two-Bit Alchemist, Sep 02 '15 at 21:32

score 2 · Accepted Answer · edited May 23 '17 at 12:07

2

Read the answers to strange result when removing item from a list to understand why this is happening.

If you really need to modify your list while iterating do this:

>>> items = ['x', 'y', 'z']
>>> while items:
...     item = items.pop()
...     print item
...
z
y
x
>>> items
[]

Note that this will iterate in reverse order.

edited May 23 '17 at 12:07

Community

answered Sep 02 '15 at 21:31

Steven Rumbalski

a way to iterate in the initial order would just be calling test_list.reverse() before running the loop – Josie Thompson Sep 02 '15 at 23:51

score 1 · Answer 2 · answered Sep 02 '15 at 21:31

1

in python this concept is called an iterator

my_iter = iter(my_list)

each time you consume or look at an element it becomes gone ...

answered Sep 02 '15 at 21:31

Joran Beasley

2 Answers2