How can I run through 2 lists at the same time in python?

Question

I am trying to print things from 2 lists one after another.

ls1 = ['Apple', 'Orange', 'Banana', 'Morty']
ls2 = ['Pineapple', 'Carrot', 'Rick', 'Tangelo']

I would usually do:

for fruit in ls1:
    print(fruit)
for fruit in ls2
    print(fruit)

but that will cycle though one list then the other. I want the output to alternate between the lists in order:

Apple
Pineapple
Orange
...etc...

or

ls1[0]
ls2[0]
ls1[1]
ls2[1]
...etc...

If list are of different size take a look into: https://stackoverflow.com/a/19686624/5916727 — niraj, Jul 18 '17 at 04:44

score 5 · Answer 1 · edited Aug 14 '17 at 05:21

5

IMHO a more pythonic way would be:

ls_1 = ["Apple", "Orange", "Banana", "Morty"]
ls_2 = ["Pineapple", "Carrot", "Rick", "Tangelo"]

for i, j in zip(ls_1, ls_2):
    print(i, j)

edited Aug 14 '17 at 05:21

RinkyPinku

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answered Jul 18 '17 at 04:44

igortg

150
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score 3 · Accepted Answer · answered Jul 18 '17 at 04:34

3

for i in range(len(ls1)):
    print(ls1[i])
    print(ls2[i])

given if length of ls1 is equal to length of ls2

answered Jul 18 '17 at 04:34

Nimish Bansal

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zip would be preferred, I think – OneCricketeer Jul 18 '17 at 04:37
Agree with @cricket_007 you got lucky that OP's real life scenario is such that both lists are of equal length. Not only does your answer lack robustness its also non-pythoninc – RinkyPinku Aug 14 '17 at 04:04
I know that but I just tried to be simple for the beginner.Thats it – Nimish Bansal Aug 14 '17 at 04:07

Rahul · Answer 3 · 2019-10-04T04:00:02.890

3

Zip is more reliable here

for i, j in zip(ls1, ls2):
    print(i)
    print(j)

zip takes care if your list are not of same length.

it stops at the length of a shorter list.

edited Oct 04 '19 at 04:00

answered Jul 18 '17 at 04:39

Rahul

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score 2 · Answer 4 · answered Jul 18 '17 at 04:41

2

I would take care of different sizes of both the list scenario too.

ls1 = ['Apple', 'Orange', 'Banana', 'Morty', 'Cherries', 'Avacado']
ls2 = ['Pineapple', 'Carrot', 'Rick', 'Tangelo']

for i in range(max(len(ls1), len(ls2))):
    if (i < len(ls1)):
        print(ls1[i])
    if (i < len(ls2)):
        print(ls2[i])

answered Jul 18 '17 at 04:41

JRG

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Nice but not pythonic, see answer of @itghisi – RinkyPinku Aug 14 '17 at 04:06

How can I run through 2 lists at the same time in python?

4 Answers4