[Python-Dev] Tricky way of of creating a generator via a comprehension expression

[Ivan Levkivskyi]

On 23 November 2017 at 13:30, Antoine Pitrou <solipsis at pitrou.net> wrote:

> On Thu, 23 Nov 2017 14:17:32 +0200
> Serhiy Storchaka <storchaka at gmail.com> wrote:
> >
> > I used the "yield" statement, but I never used the "yield" expressions.
> > And I can't found examples. Could you please present a real-world use
> > case for the "yield" (not "yield from") expression?
>
> Of course I can.  "yield" expressions are important for writing
> Python 2-compatible asynchronous code while avoiding callback hell:
>
> See e.g. http://www.tornadoweb.org/en/stable/gen.html
>
> <https://mail.python.org/mailman/listinfo/python-dev>


Great, so I open this page and see this code:

results = []
for future in list_of_futures:
    results.append(yield future)

Interesting, why don't they use a comprehension for this and instead need
to invent a whole `tornado.gen.multi` function?

--
Ivan
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