Can the value of both the current and next item be accessed in a Python list comprehension?

Question

Let's say I want to built a list of tuples from a given list. Is there any way of doing this with a list comprehension, or do I need to resort to a for loop?

[a,b,c,d,e] => [(a,b),(b,c),(c,d),(d,e)]

There is a way of doing this with a list comprehension. – jonrsharpe Sep 03 '14 at 15:32 — jonrsharpe, Sep 03 '14 at 15:32

score 2 · Accepted Answer · answered Sep 03 '14 at 15:33

2

You could do:

>>> l = ['a','b','c','d','e']
>>> [(l[i],l[i+1]) for i in range(len(l)-1)]
[('a', 'b'), ('b', 'c'), ('c', 'd'), ('d', 'e')]

with zip:

>>> zip(l,l[1:])
[('a', 'b'), ('b', 'c'), ('c', 'd'), ('d', 'e')]

-- Edited according to comments

answered Sep 03 '14 at 15:33

fredtantini

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Just `zip(l, l[1:])` will do. – Martijn Pieters Sep 03 '14 at 15:35
Very nice and Pythonic solution, in that it doesn't refer directly to anything other than the list object itself :) – Dan Lenski Sep 03 '14 at 15:36

score 0 · Answer 2 · answered Sep 03 '14 at 15:35

Not directly, but it's easy to do given a loop index, e.g.:

l='''a,b,c,d,e'''.split(',')
[(l[x],l[x+1]) for x in range(len(l)-1)]

Outputs:

[('a', 'b'), ('b', 'c'), ('c', 'd'), ('d', 'e')]

EDIT: Looks like several of us came up with this identical solution simultaneously...

Can the value of both the current and next item be accessed in a Python list comprehension?

2 Answers2