Re: [Python-ideas] gevent-like Coroutines in Python

Python's coroutines are designed to make suspension points visible, which enhances "local reasoning" about code. This concept has been written up very well over here: https://glyph.twistedmatrix.com/2014/02/unyielding.html On Tue, Oct 30, 2018 at 8:37 AM Ron Reiter wrote:

You are right that they are different, I was actually assuming that developers by default don't try to parallelize and would rather go ahead and write code to yield one function at a time, which is fine. The need to separate "await" from the invocation is something which is rarely used. Not sure what you mean about "threading" as it is still more efficient and lightweight to parallelize workers on an event loop rather than using blocking threads.

As I said - I don't think we should downgrade Python's current ability to do so, my suggestion is to create something like the "codef" proposal, which will also await on every function invocation - for readability.

- Ron

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On Tue, Oct 30, 2018 at 12:41 PM Chris Angelico wrote:

...

On Tue, Oct 30, 2018 at 6:01 PM Ron Reiter wrote:

...

... most developers would always mean they prefer to do this:

result = [await fun(x) for fun in funcs]

versus:

result = [fun(x) for fun in funcs] await asyncio.gather(*result)

Moreso, having it become the default makes statements like this:

result = [await fun(x) for fun in funcs if await smth]

Look like this:

result = [fun(x) for fun in funcs if smth]

Therefore, my suggestion is to create a new "async" definition which

basically turns every function invocation into an "await" if a generator is returned.

...

I'm not sure what you're driving at here. From your first example, I gather that (pun intended) you're expecting the 'result' list to contain all the results from the different function calls, running them all in parallel; but your second example and described suggestion seem to imply that the waitings would continue to be sequential.

Unless you're asking for straight-up magic ("do everything in parallel unless they need to be serialized"), there still needs to be a clear way to differentiate between "wait for this right now and give me a result before this function continues" and "gather all these jobs together, get me the results, and then move on once you have them all". It might perhaps be nice to have an easier/more obvious syntax for gather(), but it definitely needs to have some form of spelling.

If you're not asking for them to be run in parallel, you're asking for an implicit way for a function call to block its caller, and for the calling function to act sequentially. Python already has that - it's called threading :)

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