On Fri, Feb 23, 2018 at 10:45 AM, Guido van Rossum <[email protected]> wrote:
> There are useful things you can only do with comprehensions if the second
> for-loop can use the variable in the first for-loop. E.g.
>
> [(i, j) for i in range(10) for j in range(i)]
>
indeed -- and that is fairly common use-case in nested for loops -- so good
to preserve this.
But I still think the original:
[g(y) for x in range(5) for y in [f(x)]]
Is always going to be confusing to read. Though I do agree that it's not
too bad when you unpack it into for loops:
In [89]: for x in range(5):
...: for y in [f(x)]:
...: l.append(g(y))
BTW, would it be even a tiny bit more efficient to use a tuple in the inner
loop?
[g(y) for x in range(5) for y in (f(x),)]
-CHB
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