group_by_n.py

#!/usr/bin/env python

def group_by_n(iter_or_collection, n):
    """ This function returns iterator which iterates over tuples by n
        >>> rr = 'abcdefghijklmnopqrstuvwxyz'
        >>> for i in group_by_n(rr, 3):
        ...     print tuple(i)
        ('a', 'b', 'c')
        ('d', 'e', 'f')
        ('g', 'h', 'i')
        ('j', 'k', 'l')
        ('m', 'n', 'o')
        ('p', 'q', 'r')
        ('s', 't', 'u')
        ('v', 'w', 'x')
        ('y', 'z')
    """
    from itertools import groupby, count, izip, imap
    return ((item[1] for item in row[1])
                     for row in
             groupby(izip(count(0), iter_or_collection), lambda v: v[0]/n))

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