from itertools import islice, chain, repeat
def iterblocks(iterable, size, **kwds):
'''Break an iterable into blocks of a given size.
The optional keyword parameters determine the type of each block and what to
do if the last block has smaller size (by default return it as is).
@keyword blocktype: A callable f(iterable) for generating each block (tuple
by default).
@keyword truncate: If true, drop the last block if its length is less than
`size`.
@keyword pad: If given, the last block is padded with this object so that
is length becomes equal to `size`.
@returns: An iterator over blocks of the iterable.
>>> list(iterblocks(xrange(7), 3))
[(0, 1, 2), (3, 4, 5), (6,)]
>>> list(iterblocks(xrange(7), 3, truncate=True))
[(0, 1, 2), (3, 4, 5)]
>>> list(iterblocks(xrange(7), 3, pad=None))
[(0, 1, 2), (3, 4, 5), (6, None, None)]
>>> list(iterblocks('abcdefg', 3, pad='-', blocktype=''.join))
['abc', 'def', 'g--']
'''
truncate = kwds.get('truncate',False)
blocktype = kwds.get('blocktype',tuple)
if truncate and 'pad' in kwds:
raise ValueError("'truncate' must be false if 'pad' is given")
iterator = iter(iterable)
while True:
block = blocktype(islice(iterator,size))
if not block:
break
if len(block) < size:
if 'pad' in kwds:
block = blocktype(chain(block, repeat(kwds['pad'],
size-len(block))))
elif truncate:
break
yield block
