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

[Barry Warsaw]

On Apr 21, 2015, at 01:26 PM, Yury Selivanov wrote:

>The updated version of the PEP should be available shortly at
>https://www.python.org/dev/peps/pep-0492 and is also pasted in this email.

There's a lot to like about PEP 492.  I only want to mildly bikeshed a bit on
the proposed new syntax.

Why "async def" and not "def async"?

My concern is about existing tools that already know that "def" as the first
non-whitespace on the line starts a function/method definition.  Think of a
regexp in an IDE that searches backwards from the current line to find the
function its defined on.  Sure, tools can be updated but it is it *necessary*
to choose a syntax that breaks tools?

    def async useful():

seems okay to me.

Probably the biggest impact on the PEP would be symmetry with asynchronous
with and for.  What about:

    with async lock:

and

    for async data in cursor:

That would also preserve at least some behavior of existing tools.

Anyway, since the PEP doesn't explicitly describe this as an alternative, I
want to bring it up.

(I have mild concerns about __a*__ magic methods, since I think they'll be
harder to visually separate, but here the PEP does describe the __async_*__
alternatives.)

Cheers,
-Barry
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