[Python-Dev] async/await in Python; v2

[Victor Stinner]

Greg Ewing <greg.ewing <at> canterbury.ac.nz> writes:
> I still don't like the idea of hijacking the generic
> term "coroutine" and using it to mean this particular
> type of object.

    There are only two hard things in Computer Science: cache invalidation
and naming things.

    -- Phil Karlton

:-)

When reviewing Yury's PEP, I read Wikipedia's article of Coroutine because I
didn't know if a "coroutine" is something new in Python nor if it was well
defined.

https://en.wikipedia.org/wiki/Coroutine

Answer: it's not new, and it's implemented in many languages, and it's well
defined.

But coroutines are not always directly called "coroutines" in other
programming languages.

Using a custom name like "cofunction" may confuse users coming from other
programming languages. I prefer to keep "coroutine", but I agree that we
should make some effort to define the different categories of "Python
coroutines". Well, there are two kind kinds of coroutines:

(A) asyncio coroutine in Python 3.4: use yield from, yield denied, decorated
with @asyncio.coroutine
(B) PEP 492 coroutine in Python 3.5: use await, yield & yield from denied,
function definition prefixed by "async"

Yury proposed "generator-based coroutine for the kind (A). Maybe not a great
name, since we can learn in the PEP 492 that the kind (B) is also
(internally) based on generators.

I don't think that we should use distinct names for the two kinds in common
cases. But when we need to clearly use distinct names, I propose the
following names:

Kind (A):

- "yield-from coroutines" or "coroutines based on yield-from"
- maybe "asyncio coroutines"
- "legacy coroutines"?

Kind (B):

- "awaitable coroutines" or "coroutines based on await"
- "asynchronous coroutine" to remember the "async" keyword even if it sounds
wrong to repeat that a coroutine can be interrupted (it's almost the
definition of a coroutine, no?)
- or just "asynchronous function" (coroutine function) & "asynchronous
object" (coroutine object)

Victor