n-tuple

ntuple.py

from itertools import izip, tee

def ntuple(it, n):
    its = tee(it, n)
    for c, i in enumerate(its):
        for j in range(c): i.next()
    return izip(*its)

result

In [5]: for i in f('123456789', 1): print i
('1',)
('2',)
('3',)
('4',)
('5',)
('6',)
('7',)
('8',)
('9',)

In [6]: for i in f('123456789', 2): print i
('1', '2')
('2', '3')
('3', '4')
('4', '5')
('5', '6')
('6', '7')
('7', '8')
('8', '9')

In [7]: for i in f('123456789', 3): print i
('1', '2', '3')
('2', '3', '4')
('3', '4', '5')
('4', '5', '6')
('5', '6', '7')
('6', '7', '8')
('7', '8', '9')

In [8]: for i in f('123456789', 5): print i
('1', '2', '3', '4', '5')
('2', '3', '4', '5', '6')
('3', '4', '5', '6', '7')
('4', '5', '6', '7', '8')
('5', '6', '7', '8', '9')

In [9]: for i in f('123456789', 9): print i
('1', '2', '3', '4', '5', '6', '7', '8', '9')