On 2020-02-11 4:33 a.m., Ben Rudiak-Gould wrote:
On Mon, Feb 10, 2020 at 9:50 AM Andrew Barnert via Python-ideas
<python-ideas@python.org> wrote:
> It’s a well-known problem that async is “contagious”: [...]
>
> But C# and every other language that’s borrowed the idea has the same
problem, and as far as I know, nobody’s thought of a good answer yet.
Threads don't have that problem: you can use non-thread-aware code
with callbacks in your threaded program if you do your own locking.
Haskell (GHC) doesn't have that problem: it has fibers that use a
programming interface like C#/Python threads, but they're multiplexed
by user-mode code within a single OS thread. 16-bit Windows didn't
have that problem. Stackless and greenlet don't have that problem.
It's a problem that can be solved by just doing the obvious thing, the
thing that Python already did with threads: don't define a novel
syntax for coroutines, but instead use the syntax that already
existed.
Async/await syntax is a static type system with two types, may-yield
and will-not-yield. There's no provision for writing
generic/polymorphic code over those types, so you have to write
everything twice. Like any static type system it has some benefits,
but I don't think it's worth the cost, especially in Python, which has
always eschewed mandatory static typing.
I don't know how to fix Python now that it's gone so thoroughly down
this path (starting with the yield keyword 18 years ago). But it's not
a problem that ever needed to exist. Coroutines aren't that hard.
I would suggest having an "await in" operator. Or an "autowait" function:
def autowait(value):
if is_awaitable(value): return value
async def force_await():
return value
return force_await()
This would allow one to write "async-ready" code while calling non-async
functions.
-- Ben
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