Convert a flat list to list of lists in python

Question

One may want to do the contrary of flattening a list of lists, like here: I was wondering how you can convert a flat list into a list of lists.

In numpy you could do

Answer 1

This is usually done using the grouper recipe from the itertools documentation:

def grouper(n, iterable, fillvalue=None):
    "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
    args = [iter(iterable)] * n
    return itertools.izip_longest(fillvalue=fillvalue, *args)

Example:

>>> my_list = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
>>> list(grouper(2, my_list))
[('a', 'b'), ('c', 'd'), ('e', 'f'), ('g', None)]