[Chris Angelico <ros...@gmail.com>]
> ...
> For it to be accepted, you have to convince people - particularly,
> core devs - that it's of value. At the moment, I'm unconvinced, but on
> the other hand, all you're proposing is a default value for a
> currently-mandatory argument, so the bar isn't TOO high (it's not like
> you're proposing to create a new language keyword or anything!).
Except it's not that simple:
def gen(hi):
i = 0
while i < hi:
yield i
i += 1
from itertools import compress
g = gen(12)
print(list(filter(None, g)))
g = gen(12)
print(list(compress(g, g)))
Which displays:
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
[0, 2, 4, 6, 8, 10]
The first is obviously intended, but the latter is what you get merely
by giving the same argument twice to `complress()`.
`compress()` can't materialize its argument(s) into a list (or tuple)
first, because it's intended to work fine with infinite sequences. It
could worm around that like so:under the covers:
from itertools import tee
g = gen(12)
print(list(compress(*tee(g))))
but that's just bizarre ;-) And inefficient.
Or perhaps the `compress()` implementation could grow internal
conditionals to use a different algorithm if the second argument is
omitted. But that would be a major change to support something that's
already easily done in more than one more-than-less obvious way.
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