How do I iterate through a list whilst removing any zero from the list?

Question

I have a list that I'm trying to iterate through while removing zeros(0) if any from the list.

The following is the code:

list = [1, 2, 0, 4, 5]

for i in range(len(list)):
    if i == 0:
        list.remove(i)
    print(list[i])

Yes, the code works but raises the error IndexError: list index out of range as bellow:

1 2 4 5 Traceback (most recent call last): File "M:/Python Workspace/PycharmProjects/untitled/scrapyard.py", line 6, in print(l[i]) IndexError: list index out of range

How do I do away with this error? Thanks.

check this post: https://stackoverflow.com/questions/1207406/how-to-remove-items-from-a-list-while-iterating — Azarkuz, Oct 25 '21 at 11:48
The other way is working from the back, if you insist to use `for-loop` — Daniel Hao, Oct 25 '21 at 12:35

score 2 · Answer 1 · answered Oct 25 '21 at 11:46

2

You can use list comprehension to build a new list from your list excluding zeros:

lst = [1, 2, 0, 4, 5]
a = [x for x in lst if x !=0]
print(a)

Output:

[1, 2, 4, 5]

You can iterate directly through a.

answered Oct 25 '21 at 11:46

Tranbi

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I was removing zeros so as to multiply the items in the list. How do I proceed to multiply the items in **a** – d0ntr13 Oct 25 '21 at 12:07
you have several ways of doing this. the simplest is probably with `math.prod(a)` (import the math module before) – Tranbi Oct 25 '21 at 12:14
I wasn't remembering that. Thank you. – d0ntr13 Oct 25 '21 at 12:27

score 1 · Answer 2 · 2021-10-25T11:49:02.730

1

With your code you go to remove an element and consequently the length of the list is changed. In order to remove any zero from the function you can run the following code:

A way is this:

l = [1, 2, 0, 4, 5]

for i in range(0,l.count(0)):
    l.remove(0)

Unlike the other ways that others have proposed to you where you go to create copies of the list, with the code I wrote you you go to work on the same list without creating a new list.

edited Oct 25 '21 at 11:49

answered Oct 25 '21 at 11:42

Your code solves my issue. Thank you> – d0ntr13 Oct 25 '21 at 11:48
I hope I was helpful. If so, if you can value my answer it would be a pleasure. – Oct 25 '21 at 11:50

score 0 · Answer 3 · answered Oct 25 '21 at 13:17

The reason is you are iterating using index and also removing the elements thereby dynamically changing the length of the list. One of the approaches can be iterate through each element and remove it if it is 0:

list1 = [1, 2, 0, 4, 5]
for elem in list1:
    if elem == 0:
        list1.remove(elem)
print (list1)

Also note, it's a bad practice to use list as variable name as list is a built-in data structure name in python

How do I iterate through a list whilst removing any zero from the list?

3 Answers3

A way is this: