split list to 3 parts

Question

I have objects list:

l = [1, 2, 3, 4, 5, 6]

but they split like this:

[1, 2] [3, 4] [5, 6]

i need split list like this:

l1 = [1, 4]
l2 = [2, 5]
l3 = [3, 6]

Please, help build right templatetag.

What have you tried before asking? Did you try to change the snippet to get what you want? — Maxime Lorant, Jun 04 '14 at 12:03
In that linked question, many answers will show you how to do it the way you don’t want to, but there are some, for example [this one](http://stackoverflow.com/questions/312443/how-do-you-split-a-list-into-evenly-sized-chunks-in-python/21767522#21767522) which will give you your desired output. — poke, Jun 04 '14 at 12:10
Is this question about splitting the list (try `[[l[k] for k in range(i, len(l), N)] for i in range(N)]`) or about building the Django template? — tobias_k, Jun 04 '14 at 12:11
Also: [Equally distribute a list in python](http://stackoverflow.com/questions/22905030/equally-distribute-a-list-in-python) — poke, Jun 04 '14 at 12:12
http://stackoverflow.com/users/1433392/maxime-lorant of course i try.. but have errors, maybe i not good understand how templatetags works — macgera, Jun 04 '14 at 13:29

timgeb · Answer 1 · 2014-06-04T12:29:30.743

You could gather your lists l1, l2 l3 in another list using a list comprehension, and afterwards do something to them. For example:

l = [1, 2, 3, 4, 5, 6]
x = [[l[i]] + [l[i+3]] for i in range(len(l) - 3)]
for a in x:
    print(a)

will get you

[1, 4]
[2, 5]
[3, 6]

If you know x contains three lists, you can assign l1, l2, l3 with

l1, l2, l3 = x

Of course, you could just manually assign l1, l2, l3 too.

l1 = [l[0]] + [l[3]]
...

pacholik · Answer 2 · 2014-06-04T13:50:22.900

1

h = int(len(l)/2)
l1, l2, l3 = zip( l[:h], l[h:] )

l[:h] is the first half and l[h:] the second half. See list slices.

>>> l[:h], l[h:]
([1, 2, 3], [4, 5, 6])

Then the zip function, see zip.

>>> zip([1, 2, 3], [4, 5, 6])
[(1, 4), (2, 5), (3, 6)]

edited Jun 04 '14 at 13:50

answered Jun 04 '14 at 12:26

pacholik

It splits the original list in two and zips them together. Clever, but lacks an explanation. – Davidmh Jun 04 '14 at 12:53
This is a clever solution for the example problem, but fails for `l == [1,2,3,4,5,6,7]` assuming that the OP wants to get `[1,4], [2,5], [3,6], [4,7]` for such a list. Also, your `l1, l2, l3` are tuples (which of course could be changed to lists easily). – timgeb Jun 04 '14 at 13:30

2 Answers2