[Python-Dev] PEP 492: async/await in Python; v3

[Greg Ewing]

Yury Selivanov wrote:

>> Won't that prevent some existing generator-based
>> coroutines (ones not decorated with @coroutine)
>> from calling ones implemented with 'async def'?
>>
> It would.  But that's not a backwards compatibility
> issue.

It seems to go against Guido's desire for the new
way to be a 100% drop-in replacement for the old
way. There are various ways that old code can end
up calling new code -- subclassing, callbacks,
etc.

It also means that if person A writes a library
in the new style, then person B can't make use
of it without upgrading all of their code to the
new style as well. The new style will thus be
"infectious" in a sense.

I suppose it's up to Guido to decide whether it's
a good or bad infection. But the same kind of
reasoning seemed to be at least partly behind
the rejection of PEP 3152.

-- 
Greg