Iterate over list taking three items at a time

Question

If I have a list with:

["A","Bb","C","D","E","F","G"]

how can I iterate over it so that I can output the following:

"A Bb C"
"D E F"
"G"

"C" should be output twice? – falsetru Aug 23 '13 at 09:41 — falsetru, Aug 23 '13 at 09:41
@Haidro `"G"` was *over(ite)rated*.. – halirutan Aug 23 '13 at 09:42 — halirutan, Aug 23 '13 at 09:42
@Haidro Sorry, I've fixed my question – Baz Aug 23 '13 at 09:43 — Baz, Aug 23 '13 at 09:43

score 6 · Answer 1 · answered Aug 23 '13 at 09:43

6

Get sublists of [0:3], [3:6], [6:9], ...

>>> xs = ["A","Bb","C","D","E","F","G"]
>>> [' '.join(xs[i:i+3]) for i in range(0, len(xs), 3)]
['A Bb C', 'D E F', 'G']

answered Aug 23 '13 at 09:43

falsetru

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score 6 · Answer 2 · answered Aug 23 '13 at 09:45

6

Is a recipe that I keep hanging around.

def chunks(l, n):
    for i in xrange(0, len(l), n):
        yield l[i:i+n]

answered Aug 23 '13 at 09:45

Jakob Bowyer

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I like this the best so far but is there any way to use the itertools functions? – Noel Evans Aug 23 '13 at 09:46
1

Not directly. This might be a nice addition to itertools. – Jakob Bowyer Aug 23 '13 at 09:47
@NoelEvans Just added one :) – TerryA Aug 23 '13 at 09:48

score 3 · Answer 3 · answered Aug 23 '13 at 09:47

3

You can use itertools.izip_longest here:

>>> from itertools import izip_longest
>>> L = ["A","Bb","C","D","E","F","G"]
>>> for item in izip_longest(*[iter(L)]*3, fillvalue=''):
...     print ' '.join(item)
... 
A Bb C
D E F
G

answered Aug 23 '13 at 09:47

TerryA

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Looks more "magical" than writing it simply – Jakob Bowyer Aug 23 '13 at 09:49
the problem is that the last item is `('G', '', '')` and produces `'G '` – newtover Aug 23 '13 at 10:02
@newtover If this is a problem, you can always call `strip()` at the end :) – TerryA Aug 23 '13 at 10:04

Iterate over list taking three items at a time

3 Answers3