On 04/01/2015 12:50 AM, Jim Mooney wrote:
I'm looking at this and can't see how it works, although I understand
zipping and unpacking. The docs say it's a Python idiom. Does "idiom" mean
it works in a special way so I can't figure it out from basic principles?
It looks to me like the iterator in the list gets doubled, so the zip
should make it [(1,1),(2,2),(3,3),... ], not [(1,2),(3,4),...]
What am I missing here?
s = [1,2,3,4,5,6,7,8]
list(zip(*[iter(s)]*2))
[(1, 2), (3, 4), (5, 6), (7, 8)]
https://docs.python.org/3/library/functions.html#zip
In that same thread, Peter Otten posted the following, which I think is
probably a bit clearer:
>>> flat_pairs = ['broadcast', '"d8on"', 'broadcast', '"d11on"']
>>> it = iter(flat_pairs)
>>> pairs = list(zip(it, it))
>>> pairs
That does exactly the same thing, but in the first one you can replace
the '2' with a variable, to make variable sized tuples.
In both cases, the trick is that the same iterator is used twice in the
expression, so even though zip is taking one from each, there are no
duplications.
If you know the original data is a list, or at least that it can do
slices, then you can do Alan's suggestion:
zip(s[::2],s[1::2])
Or you could try:
from itertools import islice
pairs = zip(islice(s, 0, 9999, 2), islice(s, 1, 9999, 2))
--
DaveA
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