On Thu, Apr 23, 2020 at 3:50 PM Eric Fahlgren <ericfahlg...@gmail.com>
wrote:
> On Wed, Apr 22, 2020 at 12:23 PM David Mertz <me...@gnosis.cx> wrote:
>
>> On Wed, Apr 22, 2020, 4:24 AM Antoine Pitrou
>>
>>> But, as far as I'm concerned, the number of times where I took
>>> advantage of zip()'s current acceptance of heteregenously-sized inputs
>>> is extremely small. In most of my uses of zip(), a size difference
>>> would have been a logic error that deserves noticing and fixing.
>>>
>>
>> Your experience is very different from mine.
>>
>
> I'm in Antoine's camp on this one. A lot of our work is data analysis,
> where we get for example simulation results as X, Y, Z components then zip
> them up into coordinate triples, so any mismatch is a bug. Having
> zip_equal as a first-class function would replace zip in easily 90% of our
> use cases, but it needs to be fast as we often do this sort of thing in an
> inner loop...
>
+1
I write a lot of standalone data-munging scripts, and expecting zipped
inputs to have equal length is a common pattern.
How, for example, to collate lines from 3 potentially large files while
ensuring they match in length (without an external dependency)? The best I
can think of is rather ugly:
with open('a.txt') as a, open('b.txt') as b, open('c.txt') as c:
for lineA, lineB, lineC in zip(a, b, c):
do_something_with(lineA, lineB, lineC)
assert next(a, None) is None
assert next(b, None) is None
assert next(c, None) is None
Changing the zip() call to zip(aF, bF, cF, strict=True) would remove the
necessity of the asserts. Moreover, the concept of strict zip or zip_equal
should be intuitive to beginners, whereas my solution of next() with a
sentinel is not. (Oh, an alternative would be checking if a.readline(),
b.readline(), and c.readline() are nonempty, but that's not much better and
wouldn't generalize to non-file iterators.)
Nathan
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