Multiple indexes iteration in Python's for loop

Question

I have 4 lists, I want to iterate through the fours at once. here's an example of what I want to achieve

I'm on Python 3.8

list1 = [1,2,3]
list2 = [10,20,30]
list3 = [44,55,66]
list4 = ['a', 'b', 'c']

for i,j,k,,l in (list1, list2, list3, list4):
    print(i,j,k,l)

Output:

1, 10, 44, a
2, 20, 55, b
3, 30, 66, c

How can I achieve that ?

Thanks,

score 2 · Answer 1 · answered Jan 15 '21 at 14:35

You are looking for this:

list1 = [1,2,3]
list2 = [10,20,30]
list3 = [44,55,66]
list4 = ['a', 'b', 'c']

for i in range(len(list1)):
    print(list1[i], list2[i], list3[i], list4[i])

You loop through using a loop counter i, which is a list index. Then, you index each of the lists at that index to retrieve the values.

You may also want to read more about the range() function in Python, which in this case returns a sequence of numbers starting at 0 and finishing at len(list1) - 1, allowing you to loop through using i as an index.

Thanks for your answer, I was looking for a way more 'elegant' way to do it, I know how to do it with 2 indexes (for i,j in zip(list1, list2), ans was looking out of curiosity if you can do it for more than 2 lists — Hamouza, Jan 15 '21 at 14:40

Nic Laforge · Answer 2 · 2021-01-15T15:32:41.027

2

Use zip to combine each list together and iterate through them

list1 = [1,2,3]
list2 = [10,20,30]
list3 = [44,55,66]
list4 = ['a', 'b', 'c']

for values in zip(list1, list2, list3, list4):
    print(*values)

Output:

1 10 44 a
2 20 55 b
3 30 66 c

As values will contain a tuple, the * will unpack it for you.

edited Jan 15 '21 at 15:32

answered Jan 15 '21 at 14:40

Nic Laforge

1,776
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What If I don't want to print them, I want to do something different with each index ? – Hamouza Jan 15 '21 at 14:41
```values``` in this case contains the first element of each list, you can do what ever you want, print was only based on your example. – Nic Laforge Jan 15 '21 at 14:43
2

"values will contain a list" => should be a tuple – costaparas Jan 15 '21 at 14:48

score 2 · Answer 3 · answered Jan 15 '21 at 14:44

2

Not sure if this is what you are looking for but we can zip all 4 list and read them:

for i in zip(list1,list2,list3,list4):
    print(i)

answered Jan 15 '21 at 14:44

Divyaansh Bajpai

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score -2 · Accepted Answer · answered Jan 15 '21 at 14:59

Come in late, all prev. posts have done great answering the question. Here is to sum up and answer - what if I want to different ordering on the 4 items:

>>> for value_tpl in zip(list1, list2, list3, list4):
    n1, n2, n3, label = value_tpl
    print(label, n3, n2, n1)

    
A 44 10 1
B 55 20 2
C 66 30 3

Multiple indexes iteration in Python's for loop

4 Answers4