[Python-Dev] PEP 492: No new syntax is required (original) (raw)

Guido van Rossum guido at python.org
Tue Apr 28 22:00:26 CEST 2015

On Tue, Apr 28, 2015 at 11:51 AM, Stefan Behnel <stefan_ml at behnel.de> wrote:

Mark Shannon schrieb am 27.04.2015 um 09:48: > On 27/04/15 00:13, Guido van Rossum wrote: >> Currently this means looking for yield [from]; PEP 492 just adds looking >> for await and async [for|with]. Making await() a function defeats the >> purpose because now aliasing can hide its presence, and we're back in >> the land of gevent or stackless (where anything can potentially >> suspend the current task). I don't want to live in that land. > > I don't think I was clear enough. I said that "await" is a function, not > that is should be disguised as one. Reading the code, "GetAwaitableIter" > would be a better name for that element of the implementation. It is a > straightforward non-blocking function.

1) it's not like people commonly alias "repr()" or "len()", so why would they alias an "await()" builtin ? Unless, obviously, there's an actual reason to do so, in which case having it as a functions comes in handy. :) We had the same line of reasoning with "print()" back in the days of Py3k. 2) an "await()" builtin function that calls an "await()" special method on its input object sounds very pythonic.

This sounds confused. The await expression must be recognized by the parser so it can generate different code for it (the code to suspend the stack). A builtin function cannot generate different code -- to the compiler all functions look the same. I know we could change that rule, but that' would be a really a big deviation from Python's philosophy: Currently the code generator never needs to know the type of any variables -- and a builtin function 'await' would just be another variable to the code generator.

-- --Guido van Rossum (python.org/~guido) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20150428/3680df3e/attachment.html>

More information about the Python-Dev mailing list