Earlier quoted context omitted.
Sure, there are many ways to do it, but I think the author was going for speed here.
Did you test and time the itertools version?
I did not, but I might now.
EDIT: See update above.
Brilliant or insane code?
21–30 of 114 posts
Re: Brilliant or insane code?
#22i = iter(array) return zip(i, i, i) There you go. All but neceessary magic gone with just one line more.
A much clearer solution, I would also add a comment reminding people how zip works.
Re: Brilliant or insane code?
#23Earlier quoted context omitted.
I'd be surprised if my way is slower. Any time you unpack into a function such as zip() python has to create an intermediary list to store all the results before calling the function.
You could always use izip: http://docs.python.org/2/library/itertools.html#itertools.iz...
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Re: Brilliant or insane code?
#24It does not rely on an implementation detail, that is how iterators work. He's just supplied the same iterator to a function which consumes iterators... that's exactly the expected behaviour.
The fact that zip evaluates its arguments in order is an implementation detail. It could evaluate them in reverse order, in which case this code would not behave as expected.
That's what I meant, thanks for clarifying. It does seem that the zip() docs make a guarantee of left-to-right evaluation, though, so my apprehension proved unfounded.
Re: Brilliant or insane code?
#25i = iter(array) return zip(i, i, i) There you go. All but neceessary magic gone with just one line more.
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Re: Brilliant or insane code?
#26You can also do
zip(arr[::3], arr[1::3], arr[2::3])
zip(islice(arr, 0, None, 3), islice(arr, 1, None, 3), islice(arr, 2, None, 3))
Re: Brilliant or insane code?
#27We all love short and fast. But this is definitely an interesting approach. I'd love to see similar approaches to problems if you guys can point out to some.
I would also, I love this sort of thing. How about:
>>> some_boolean = False
>>> ["Thing 1", "Thing 2"][some_boolean]
"Thing 1"Re: Brilliant or insane code?
#28It's not brilliant. This accomplishes the same thing without being hard to understand: from itertools import islice iterator = iter(array) try: while True: yield list(islice(iterator, 3)) except StopIteration: pass
This crashed my computer (it's an infinite loop that needs too much memory, apparently), and there's a mistake (the i is not defined).
Turns out that islice doesn't raise an IterationError, it just returns an empty list.
Fixing the problems, it runs in 237 μsec per loop, around 23 times more than the zip version.
Re: Brilliant or insane code?
#29Earlier quoted context omitted.
I'd be surprised if my way is slower. Any time you unpack into a function such as zip() python has to create an intermediary list to store all the results before calling the function.
You could always use izip: http://docs.python.org/2/library/itertools.html#itertools.iz...
I was a bit wrong about that. For some reason I imagined that there would be quite a few args being passed to zip, when in fact there are just the three iterators. It does create a temporary list, but it's so small it's negligible. Using izip wouldn't really change anything.
Re: Brilliant or insane code?
#30It's not brilliant. This accomplishes the same thing without being hard to understand: from itertools import islice iterator = iter(array) try: while True: yield list(islice(iterator, 3)) except StopIteration: pass
This crashed my computer (it's an infinite loop that needs too much memory, apparently), and there's a mistake (the i is not defined). Turns out that islice doesn't raise an IterationError, it just returns an empty list. Fixing the problems, it runs in 237 μsec per loop, around 23 times more than the zip version.
Haha. I feel very silly now. I was just about to respond with the same thing.
while True:
result = list(islice(iterator, 3))
if not result:
break
yield result