import itertools


def partitionby(func, seq):
    """ Partition a sequence according to a function

    Partition `s` into a sequence of lists such that, when traversing
    `s`, every time the output of `func` changes a new list is started
    and that and subsequent items are collected into that list.

    >>> is_space = lambda c: c == " "
    >>> list(partitionby(is_space, "I have space"))
    [('I',), (' ',), ('h', 'a', 'v', 'e'), (' ',), ('s', 'p', 'a', 'c', 'e')]

    >>> is_large = lambda x: x > 10
    >>> list(partitionby(is_large, [1, 2, 1, 99, 88, 33, 99, -1, 5]))
    [(1, 2, 1), (99, 88, 33, 99), (-1, 5)]

    See also:
        partition
        groupby
        itertools.groupby
    """
    # Note: applying `list` seems to be required both Python 2 and 3
    # compatible (Python 3 works without it).
    return (tuple(v) for k, v in itertools.groupby(seq, key=func))