[Python-Dev] A more flexible task creation

[Michel Desmoulin]

> 
> The strict API compatibility requirements of core Python stdlib, coupled
> with the very long feature release life-cycles of Python, make me think
> this sort of thing perhaps is better built in an utility library on top
> of asyncio, rather than inside asyncio itself?  18 months is a long long
> time to iterate on these features.  I can't wait for Python 3.8...
>  

A lot of my late requests come from my attempt to group some of that in
a lib: https://github.com/Tygs/ayo

Most of it works, although I got read of context() recently, but the
lazy task part really fails.


Indeed, the API allows to do:

        async with ayo.scope() as run:
            task_list = run.all(foo(), foo(), foo())
            run.asap(bar())
            await task_list.gather()
            run.asap(baz())



scope() return a nursery like object, and this works perfectly, with the
usual guaranty of Trio's nursery, but working in asyncio right now.

However, I tried to add to the mix:

        async with ayo.scope(max_concurrency=2) as run:
            task_list = run.all(foo(), foo(), foo())
            run.asap(bar())
            await task_list.gather()
            run.asap(baz())

And I can get it to work. task_list will right now contains a list of
tasks and None, because some tasks are not scheduled immediately. That's
why I wanted lazytasks. I tried to create my own lazy tasks, but it
never really worked. I'm going to try to go down the road of wrapping
the unscheduled coro in a future-like object as suggested by Yuri. But
having that built-in seems logical, elegant, and just good design in
general: __init__ should not have side effects.