["python","algorithm","generator","chunking"]
how to split an iterable in constant-size chunks

I am surprised I could not find a "batch" function that would take as input an iterable and return an iterable of iterables. For example: for i in batch(range(0,10), 1): print i [0] [1] ... [9] or: for i in batch(range(0,10), 3): print i [0,1,2] [3,4,5] [6,7,8] [9] Now, I wrote what I thought was a pretty simple generator: def batch(iterable, n = 1): current_batch = [] for item in iterable: current_batch.append(item) if len(current_batch) == n: yield current_batch current_batch = [] if current_batch: yield current_batch But the above does not give me what I would have expected: for x in batch(range(0,10),3): print x [0] [0, 1] [0, 1, 2] [3] [3, 4] [3, 4, 5] [6] [6, 7] [6, 7, 8] [9] So, I have missed something and this probably shows my complete lack of understanding of python generators. Anyone would care to point me in the right direction ? [Edit: I eventually realized that the above behavior happens only when I run this within ipython rather than python itself]
This is probably more efficient (faster) def batch(iterable, n=1): l = len(iterable) for ndx in range(0, l, n): yield iterable[ndx:min(ndx + n, l)] for x in batch(range(0, 10), 3): print x Example using list data = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] # list of data for x in batch(data, 3): print(x) # Output [0, 1, 2] [3, 4, 5] [6, 7, 8] [9, 10] It avoids building new lists.