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Created on2019-02-19 23:36 byDan Rose, last changed2022-04-11 14:59 byadmin. This issue is nowclosed.
| Pull Requests | |||
|---|---|---|---|
| URL | Status | Linked | Edit |
| PR 12010 | merged | python-dev,2019-02-24 06:31 | |
| Messages (5) | |||
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| msg336025 -(view) | Author: Dan Rose (Dan Rose)* | Date: 2019-02-19 23:36 | |
It is very important when using a callable to know whether it is async or not. It is expected that `builtins.help` function should provide the information needed to properly use the function, but it omits whether it is an async function or not.```import asynciodef the_answer():return 42async def the_answer2():await asyncio.sleep(100)return the_answer()``````>>> help(the_answer)Help on function the_answer in module __main__:the_answer()>>> help(the_answer2)Help on function the_answer2 in module __main__:the_answer2()```Note there is no way to tell whether the result of the function needs to be awaited.In the similar case of generator functions versus regular functions, one obvious solution is to add a type annotation. That doesn't work here, since PEP-0484 indicates that the correct annotation for a coroutine function is the type that is awaited, not the coroutine object created when the function is called.```import typingdef non_answers() -> typing.Iterable[int]: yield from range(42)>>> help(non_answers)Help on function non_answers in module __main__:non_answers() -> Iterable[int]```One awkward workaround is to wrap the coroutine function in a regular function:```def the_answer3() -> typing.Awaitable[int]: return the_answer2()>>> help(the_answer3)Help on function the_answer3 in module __main__:the_answer3() -> Awaitable[int]``` | |||
| msg336027 -(view) | Author: Raymond Hettinger (rhettinger)*![]() | Date: 2019-02-19 23:55 | |
This would be a reasonable addition to help(). Would you like to make a PR?An "async def" can be detected with inspect.iscoroutinefunction(the_answer2). | |||
| msg336046 -(view) | Author: Dan Rose (Dan Rose)* | Date: 2019-02-20 07:10 | |
Thanks for the suggestion, Raymond. I was toying with the idea of a PR, but wasn’t sure what the resolution should be, and it’s a rather subtle decision for my first contribution.It seems to me that this might be an oversight in PEP-0484, and the purest resolution is that either Generator and Coroutine should both be part of the type signature or neither should be.If the PEP is indeed correct, the help output *could* look like:async the_answer2() -> intWhich would be equivalent to the (functionally identical) wrapper:the_answer3() -> Awaitable[int]Philosophically, does asyncness belong on the left or right of the arrow? Should it change just because of how the function is expressed? | |||
| msg336047 -(view) | Author: Dan Rose (Dan Rose)* | Date: 2019-02-20 07:38 | |
Note to future self: whatever solution should also play nice with functools.partial | |||
| msg343376 -(view) | Author: miss-islington (miss-islington) | Date: 2019-05-24 11:38 | |
New changeset2a37f8f55b543589cc77a67b5cd17cbd9d0311c9 by Miss Islington (bot) (Dan Rose) in branch 'master':bpo-36045: builtins.help() now prefixes `async` for async functions (GH-12010)https://github.com/python/cpython/commit/2a37f8f55b543589cc77a67b5cd17cbd9d0311c9 | |||
| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:59:11 | admin | set | github: 80226 |
| 2019-05-24 11:38:46 | asvetlov | set | status: open -> closed resolution: fixed stage: patch review -> resolved |
| 2019-05-24 11:38:14 | miss-islington | set | nosy: +miss-islington messages: +msg343376 |
| 2019-02-24 06:31:46 | python-dev | set | keywords: +patch stage: needs patch -> patch review pull_requests: +pull_request12041 |
| 2019-02-20 07:38:48 | Dan Rose | set | messages: +msg336047 |
| 2019-02-20 07:10:16 | Dan Rose | set | messages: +msg336046 |
| 2019-02-20 02:44:52 | eamanu | set | nosy: +eamanu |
| 2019-02-19 23:55:41 | rhettinger | set | type: enhancement versions: + Python 3.8, - Python 3.7 keywords: +easy nosy: +rhettinger messages: +msg336027 stage: needs patch |
| 2019-02-19 23:39:47 | Dan Rose | set | title: Help function is not much help with async functions -> builtins.help function is not much help with async functions |
| 2019-02-19 23:36:27 | Dan Rose | create | |