On 06.09.2016 19:38, Yury Selivanov wrote:
On 2016-09-06 9:40 AM, C Anthony Risinger wrote:
On Tue, Sep 6, 2016 at 10:20 AM, Sven R. Kunze <srku...@mail.de
<mailto:srku...@mail.de>> wrote:
So, what's the "async" good for then?
Maybe I'm off base here, but my understanding is the `async for`
version would allow for suspension during the actual iteration, ie.
using the __a*__ protocol methods, and not just by awaiting on the
produced item itself.
IOW, `[await ... async for ...]` will suspend at least twice, once
during iteration using the __a*__ protocols and then again awaiting
on the produced item, whereas `[await ... for ...]` will
synchronously produce items and then suspend on them. So to use the
async + await version, your (async) iterator must return awaitables
to satisfy the `async for` part with then produce another awaitable
we explicitly `await` on.
Can someone confirm this understanding? And also that all 4
combinations are possible, each with different meaning:
# Normal comprehension, 100% synchronous and blocking
[... for ...]
# Blocking/sync iterator producing awaitables which suspend before
producing a "normal" value
[await ... for ...]
# Non-blocking/async iterator that suspends before producing "normal"
values
[... async for ...]
# Non-blocking/async iterator that suspends before producing
awaitables which suspend again before producing a "normal" value
[await ... async for ...]
Is this correct?
All correct. I'll update the PEP to better clarify the semantics.
Still don't understand what the "async" is good for. Seems redundant to me.
Sven
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