I see. Well, I woudln't expect that behaviour from such a function. On 12/08/2013 07:06 PM, Amber Yust wrote:
So does zip if the items are of unequal length, and the two code examples I provided (the one using zip and the long-form one) are equivalent.
On Sun Dec 08 2013 at 9:49:56 AM, Mathias Panzenböck <grosser.meister.morti@gmx.net <mailto:grosser.meister.morti@gmx.net>> wrote:
On 12/08/2013 05:44 AM, Amber Yust wrote: > After seeing yet another person asking how to do this on #python (and having needed to do it in the past myself), I'm > wondering why itertools doesn't have a function to break an iterator up into N-sized chunks. > > Existing possible solutions include both the "clever" but somewhat unreadable... > > batched_iter = zip(*[iter(input_iter)]*n) > > ...and the long-form... > > def batch(input_iter, n): > input_iter = iter(input_iter) > while True: > yield [input_iter.next() for _ in range(n)] >
This function drops items if the length of the input sequence is not a multiple of n. Fix:
def batch(it, n): it = iter(it) while True: slice = [] for _ in range(n): try: slice.append(it.next()) except StopIteration: if slice: yield slice return yield slice
> There doesn't seem, however, to be one clear "right" way to do this. Every time I come up against this task, I go back > to itertools expecting one of the grouping functions there to cover it, but they don't. > > It seems like it would be a natural fit for itertools, and it would simplify things like processing of file formats that > use a consistent number of lines per entry, et cetera. > > ~Amber >
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