Turn flat list into two-tuples

Question

Is there a single line expression to accomplish the following:

input = ['this', 'is', 'a', 'list']
output = [('this', 'is'), ('a', 'list')]

My initial idea was to create two lists and then zip them up. That would take three lines.

The list will have an even number of elements.

Your original plan is fine. I'm sure you could hammer it into one ugly line. — Colonel Panic, Feb 15 '13 at 20:21

score 9 · Accepted Answer · answered Feb 15 '13 at 20:23

9

This is quite short:

zip(input, input[1:])[::2]

answered Feb 15 '13 at 20:23

piokuc

The question has been marked as a duplicate, but I have't seen this answer yet :) I must say I like it... – piokuc Feb 15 '13 at 20:27
1

Note: does not work in python3. See root's answer for a python3 solution. – 00500005 Mar 12 '14 at 17:14
Interesting, thanks. – piokuc Mar 12 '14 at 18:24
1

Try ```zip(input[::2], input[1::2])``` for python3 (inspired by your answer) – NorthIsUp May 09 '17 at 22:35
@NorthIsUp nice, thanks! – piokuc May 22 '17 at 09:04

score 7 · Answer 2 · answered Feb 15 '13 at 20:25

7

In [4]: zip(*[iter(lst)]*2)
Out[4]: [('this', 'is'), ('a', 'list')]

answered Feb 15 '13 at 20:25

root

1

Does this work because you are feeding zip the same iterator twice, so after getting the first item from the "first list" the first item from the "second list" is actually the 2nd item in the original list? – flutefreak7 May 07 '15 at 20:00

score 4 · Answer 3 · answered Feb 15 '13 at 20:21

4

>>> input = ['this', 'is', 'a', 'list']

>>> [(input[i], input[i + 1]) for i in range(0, len(input), 2)]
[('this', 'is'), ('a', 'list')]

answered Feb 15 '13 at 20:21

Rohit Jain

3 Answers3