I have a list:

[a, b, c, d, e, f, g, h, i, j, k, l, m,  n, o, p]

I would like 4 lists:

[a, e, i, m]
[b, f, j, n]
[c, g, k, o]
[d, h, l, p]

How would I go about this?
Thanks.

Recommended Answers

All 10 Replies

see grouper example from itertools module documentation.

Sorry, mislead you by over simplifying the question...
The main list will have full paths to files in it, not simple one-character elements. They will vary in length significantly.

Sorry, mislead you by over simplifying the question...
The main list will have full paths to files in it, not simple one-character elements. They will vary in length significantly.

It works nonetheless. Try to call splitIt(4, yourlist).

TypeError: expected string or buffer

Are we at crossed purposes here? I don't want my list in equal pieces. I want elements 0,4,8,12 in one new list, elements 1,5,9,13 in another new list etc Or even simpler elements 0,1,2,3 elements 4,5,6,7 elements 8,9,10,11 in new lists (workable but not as elegant for me).

Are we at crossed purposes here? I don't want my list in equal pieces. I want elements 0,4,8,12 in one new list, elements 1,5,9,13 in another new list etc Or even simpler elements 0,1,2,3 elements 4,5,6,7 elements 8,9,10,11 in new lists (workable but not as elegant for me).

Oh, then try

[list(x) for x in zip(*splitIt(4, yourlist))]

Sorry, I don't understand how this generates four lists from one...

It is Python idiom for transposing values (assuming that count of elements is divisible by the row length)

>>> v = "abcdefghijklmnop"
>>> m = [a+b+c+d for a,b,c,d in zip(v[::4], v[1::4], v[2::4], v[3::4])]
>>> m
['abcd', 'efgh', 'ijkl', 'mnop']
>>> m = [a+b+c+d for a,b,c,d in zip(*zip(v[::4], v[1::4], v[2::4], v[3::4]))]
>>> m
['aeim', 'bfjn', 'cgko', 'dhlp']
>>>

One simple way to sample a list while skipping elements with with the following syntax.

a=[1,2,3,4,5]
b=a[::2]  #means sample all elements with spacing = 2
print b
>>>[1,3,5]

c=a[2::2]  #means sample all elements with spacing =2 starting from the 3rd element
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