How do I pop a stack till it's empty using a FOR loop?

Question

S=['TOM', 'HARRY', 'MAMA', 'JOE']
print(S)
for x in S:
    print(S.pop())
    if S==[]:
        print("Empty")
        break

Using a for loop should iterate through the entire list and give me all the items followed by 'Empty' but instead, it only gives two elements

What I'm getting-

['TOM', 'HARRY', 'MAMA', 'JOE']
JOE
MAMA

What I was expecting-

['TOM', 'HARRY', 'MAMA', 'JOE']
JOE
MAMA
HARRY
TOM
Empty

This is my first question here so any tips on how to frame questions would be appreciated.

***This might help:*** https://stackoverflow.com/q/6022764/12769604 — Jupri, Jun 02 '22 at 10:41

score 2 · Answer 1 · answered Jun 02 '22 at 10:04

The main issue with your code is that you can't loop over a list while doing changes to that list. If you want to use a for loop (timgeb suggestion is great btw). You could do this:

for _ in range(len(S)):
    print(S.pop())

This will take care of popping all the items of the list

score 1 · Answer 2 · answered Jun 02 '22 at 10:03

1

You see an unexpected result because you're mutating the list while iterating over it. Note that you're not doing anything with x, so a for loop is not the right tool here.

Use a while loop.

while S:
    print(S.pop())

print('empty')

answered Jun 02 '22 at 10:03

timgeb

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Functionally correct but OP specifically stated that he wants a *for* loop – DarkKnight Jun 02 '22 at 10:05
3

@AlbertWinestein OP doesn't know what he wants. – timgeb Jun 02 '22 at 10:05
@timgeb I did know that you could use a while loop, I just wanted to know why you can't use a for loop like that so thanks – Akul Chordia Jul 16 '22 at 20:33

score 0 · Answer 3 · answered Jun 02 '22 at 10:08

0

S=['TOM', 'HARRY', 'MAMA', 'JOE']
print(S)
for x in S[::-1]:
    print(S.pop())
    if S==[]:
        print("Empty")
        break

answered Jun 02 '22 at 10:08

uozcan12

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1
5
13

This won't work as you are attempting to modify a list that you are using to iterate into – EnriqueBet Jun 02 '22 at 10:11

How do I pop a stack till it's empty using a FOR loop?

3 Answers3