On 25 January 2016 at 05:57, Brett Cannon <brett@python.org> wrote:
On Sun, Jan 24, 2016, 04:55 Nick Coghlan <ncoghlan@gmail.com> wrote:
On 24 January 2016 at 15:16, Guido van Rossum <guido@python.org> wrote:
I wonder if kids today aren't too much in love with local function definitions. :-) There's a reason why executor.submit() takes a function *and arguments*. If you move the function out of the for loop and pass the url as a parameter to submit(), problem solved, and you waste fewer resources on function objects and cells to hold nonlocals.
Aye, that's how the current example code in the docs handles it - there's an up front definition of the page loading function, and then the submission to the executor is with a dict comprehension.
The only thing "wrong" with it is that when reading the code, the potentially single-use function is introduced first without any context, and it's only later that you get to see what it's for.
So the doics just need an added comment to help explain it. Want to file an issue for that?
There's nothing to comment on given the Python semantics we have today - what's there is a sensible way to write that code, and the design FAQ covers why the inline closure approach wouldn't work. As noted, I suspect the only reason the topic keeps coming up is the niggling sense that the closure based approach "should" work, and the fact that it doesn't is a case where underlying technical details that we generally aim to let people gloss over make themselves apparent. Cheers, Nick. -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia