[Python-Dev] async/await in Python; v2

[Greg Ewing]

PJ Eby wrote:
> I find this a little weird.  Why not just have `with` and `for` inside
> a coroutine dynamically check the iterator or context manager, and
> either behave sync or async accordingly?  Why must there be a
> *syntactic* difference?

It depends on whether you think it's important to
have a syntactic marker for points where the code can
potentially be suspended.

In my original vision for PEP 3152, there was no
"cocall" syntax -- you just wrote an ordinary call,
and whether to make a cocall or not was determined
at run time. But Guido and others felt that it would
be better for suspension points to be explicit, so
I ended up with cocall.

The same reasoning presumably applies to asynchronous
'for' and 'with'. If you think that it's important
to make suspendable calls explicit, you probably want
to mark them as well.

> ...which, incidentally, highlights one of the things that's been
> bothering me about all this "async foo" stuff: "async def" looks like
> it *defines the function* asynchronously

That bothers me a bit, too, but my main problem with it
is the way it displaces the function name. "def f() async:"
would solve both of those problems.

-- 
Greg