On Thu, Oct 13, 2016 at 04:34:49PM +0200, Martti Kühne wrote:
> > If I had seen a list comprehension with an unpacked loop variable:
> >
> > [t for t in [(1, 'a'), (2, 'b'), (3, 'c')]]
Marttii, somehow you have lost the leading * when quoting me. What I
actually wrote was:
[*t for t in [(1, 'a'), (2, 'b'), (3, 'c')]]
> As it happens, python does have an external consumption operation that
> happens externally with an iteration implied:
>
> for t in iterable:
> yield t
If you replace the t with *t, you get a syntax error:
py> def gen():
... for t in [(1, 'a'), (2, 'b'), (3, 'c')]:
... yield *t
File "<stdin>", line 3
yield *t
^
SyntaxError: invalid syntax
Even if it was allowed, what would it mean? It could only mean "unpack
the sequence t, and collect the values into a tuple; then yield the
tuple".
> For your example [t for t in [(1, 'a'), (2, 'b'), (3, 'c')]] that would mean:
>
> for t in [(1, 'a'), (2, 'b'), (3, 'c')]:
> yield t
>
> And accordingly, for the latter case [*t for t in [(1, 'a'), (2, 'b'),
> (3, 'c')]] it would be:
>
> for item in [(1, 'a'), (2, 'b'), (3, 'c')]:
> for t in item:
> yield t
No it wouldn't. Where does the second for loop come from? The list
comprehension shown only has one loop, not nested loops.
--
Steve
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