Splitting a python list into 4 sub-lists that are as even as possible

Question

I'm trying to split a python list into four groups that are as even as possible, so for example, if the original list was [1, 2, 3, 4, 5, 6, 7, 8], then the resulting four sub-lists would be [1, 5] [2,6] [3,7] [4,8] where the code goes through each number in the original list and assigns them to a different group, and once it reaches group 4, it goes back to assigning to group 1.

If the original list is [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] then the resulting four groups should be [1,5,9] [2,6,10] [3,7] [4,8] where two groups have 3 items, and the other two groups have 2 items--making the groups as even as possible.

Any idea how I could achieve this?

Answer is given in https://stackoverflow.com/questions/2130016/splitting-a-list-into-n-parts-of-approximately-equal-length/37414115 — IsolatedSushi, Nov 26 '20 at 20:46
@IsolatedSushi--doesn't that link produce different output than what's desired? — DarrylG, Nov 26 '20 at 20:48
I don't see why this post has -5 score. This is a perfectly good question. — new Q Open Wid, Nov 27 '20 at 15:55

Jan Christoph Terasa · Accepted Answer · 2023-06-19T10:37:41.803

3

Try this, it splits the input list into sublists in the round-robin fashion you desire:

def round_robin_sublists(l, n=4):
    lists = [[] for _ in range(n)]
    i = 0
    for elem in l:
        lists[i].append(elem)
        i = (i + 1) % n
    return lists

l = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
sublist = round_robin_sublists(l) # [[1, 5, 9], [2, 6, 10], [3, 7], [4, 8]]

edited Jun 19 '23 at 10:37

answered Nov 26 '20 at 20:55

Jan Christoph Terasa

5,781
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score 2 · Answer 2 · answered Nov 26 '20 at 20:56

2

>>> [a[i::4] for i in range(4)]
[[1, 5, 9], [2, 6, 10], [3, 7], [4, 8]]

answered Nov 26 '20 at 20:56

superb rain

5,300
2
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Wait what is the `a[i::4]` part? – orph-c Nov 26 '20 at 21:22

Splitting a python list into 4 sub-lists that are as even as possible

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