Python split list into n chunks

Use numpy

>>> import numpy
>>> x = range(25)
>>> l = numpy.array_split(numpy.array(x),6)

or

>>> import numpy
>>> x = numpy.arange(25)
>>> l = numpy.array_split(x,6);

You can also use numpy.split but that one throws in error if the length is not exactly divisible.

The solution(s) below have many advantages:

• Uses generator to yield the result.
• No imports.
• Lists are balanced (you never end up with 4 lists of size 4 and one list of size 1 if you split a list of length 17 into 5).

def chunks(l, n):
    """Yield n number of striped chunks from l."""
    for i in range(0, n):
        yield l[i::n]

The code above produces the below output for l = range(16) and n = 6:

[0, 6, 12]
[1, 7, 13]
[2, 8, 14]
[3, 9, 15]
[4, 10]
[5, 11]

If you need the chunks to be sequential instead of striped use this:

def chunks(l, n):
    """Yield n number of sequential chunks from l."""
    d, r = divmod(len(l), n)
    for i in range(n):
        si = (d+1)*(i if i < r else r) + d*(0 if i < r else i - r)
        yield l[si:si+(d+1 if i < r else d)]

Which for l = range(16) and n = 6 produces:

[0, 1, 2]
[3, 4, 5]
[6, 7, 8]
[9, 10, 11]
[12, 13]
[14, 15]

See this stackoverflow link for more information on the advantages of generators.

If order doesn't matter:

def chunker_list(seq, size):
    return (seq[i::size] for i in range(size))

print(list(chunker_list([1, 2, 3, 4, 5], 2)))
>>> [[1, 3, 5], [2, 4]]

print(list(chunker_list([1, 2, 3, 4, 5], 3)))
>>> [[1, 4], [2, 5], [3]]

print(list(chunker_list([1, 2, 3, 4, 5], 4)))
>>> [[1, 5], [2], [3], [4]]

print(list(chunker_list([1, 2, 3, 4, 5], 5)))
>>> [[1], [2], [3], [4], [5]]

print(list(chunker_list([1, 2, 3, 4, 5], 6)))
>>> [[1], [2], [3], [4], [5], []]