Group a list of items into a nested list of subgroups, where the subgroups are of a certain length. Useful e.g. if you want to display a flat list into a 2-column or 3-column layout.

groupby

#!/usr/bin/python


def groupby(iterable, groupsize=2):
    """
    Split an iterable [a, b, c, ...]
    into a nested list of tuples [(a, b), (c, ...)]
    where the length of the tuples is governed by groupsize.

    The default groupsize results in pairwise grouping:

    >>> iterable = [1,2,3,4,5,6]
    >>> groupby(iterable)
    [(1, 2), (3, 4), (5, 6)]

    If the number of items in iterable doesn't match the groupsize,
    the last returned group is incomplete:

    >>> iterable = [1,2,3,4,5]
    >>> groupby(iterable)
    [(1, 2), (3, 4), (5,)]

    We can also group by 3 instead of by 2 items:

    >>> iterable = [1,2,3,4,5,6,7]
    >>> groupby(iterable, 3)
    [(1, 2, 3), (4, 5, 6), (7,)]

    """
    result = []
    subgroup = []
    for item in iterable:
        subgroup.append(item)
        if len(subgroup) % groupsize == 0:
            result.append(tuple(subgroup))
            subgroup = []
    if len(subgroup) > 0:
        result.append(tuple(subgroup))
    return result

if __name__ == '__main__':
    import doctest
    doctest.testmod()