CODEWITHSUNDEEP
pythonfor-loop
alwbtc
alwbtc

Reputation: 29445

How to get two items at a time in a for loop in python?

Is there a way to read two items at a time in a for loop in python? If yes, what is the best way?

For example:

a = [1,2,3,4,5,6,7,8,9]

for ix, i in enumerate(a):
    j = a[ix+1]
    print("i:", i, "j:", j)

But it will fail when i reaches the last item because a[ix+1] doesn't exist. Is there a better way which will never fail?

Upvotes: 0

Views: 557

Answers (3)

Rakesh
Rakesh

Reputation: 82765

You can use itertools.zip_longest

Ex:

from itertools import zip_longest
a = [1,2,3,4,5,6,7,8,9]
for i,v in zip_longest(a, a[1:]): 
    print(i, v)

Output:

1 2
2 3
3 4
4 5
5 6
6 7
7 8
8 9
9 None

Upvotes: 1

Celius Stingher
Celius Stingher

Reputation: 18367

If you want to use the for loop, you should iterate until the -1 value:

for i in (a[:-1]):
    j = a[i+1]
    print("i:",i,"j:",j)

Upvotes: 1

iz_
iz_

Reputation: 16583

You can fix your code by slicing out the last item:

a = [1,2,3,4,5,6,7,8,9]

for ix, i in enumerate(a[:-1]):
    j = a[ix+1]
    print("i:", i, "j:", j)

A better way is to use zip:

a = [1,2,3,4,5,6,7,8,9]

for i, j in zip(a, a[1:]):
    print("i:", i, "j:", j)

Upvotes: 1

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