contextvars does not work properly in asyncio REPL.

[lanfon72]

BPO	43419
Nosy	@asvetlov, @1st1, @lanfon72
PRs	bpo-43419: fix contextvars behaviors in asyncio REPL #24773

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-03-06.14:09:53.246>
labels = ['type-bug', '3.8', '3.9', 'expert-asyncio']
title = 'contextvars does not work properly in asyncio REPL.'
updated_at = <Date 2021-03-06.15:06:01.651>
user = 'https://github.com/lanfon72'

bugs.python.org fields:

activity = <Date 2021-03-06.15:06:01.651>
actor = 'lanfon72'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['asyncio']
creation = <Date 2021-03-06.14:09:53.246>
creator = 'lanfon72'
dependencies = []
files = []
hgrepos = []
issue_num = 43419
keywords = ['patch']
message_count = 1.0
messages = ['388199']
nosy_count = 3.0
nosy_names = ['asvetlov', 'yselivanov', 'lanfon72']
pr_nums = ['24773']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue43419'
versions = ['Python 3.8', 'Python 3.9']

[lanfon72]

Demonstration (via python -m asyncio):

asyncio REPL 3.9.0 (default, Oct 18 2020, 00:21:26) 
[Clang 11.0.0 (clang-1100.0.33.16)] on darwin
Use "await" directly instead of "asyncio.run()".
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> from contextvars import ContextVar
>>> ctx = ContextVar('ctx')
>>> ctx.set(1)
<Token var=<ContextVar name='ctx' at 0x1021bbc70> at 0x1021bf800>
>>> ctx.get()
Traceback (most recent call last):
  File "/Users/lanfon/.pyenv/versions/3.9.0/lib/python3.9/concurrent/futures/_base.py", line 440, in result
    return self.__get_result()
  File "/Users/lanfon/.pyenv/versions/3.9.0/lib/python3.9/concurrent/futures/_base.py", line 389, in __get_result
    raise self._exception
  File "/Users/lanfon/.pyenv/versions/3.9.0/lib/python3.9/asyncio/__main__.py", line 34, in callback
    coro = func()
  File "<console>", line 1, in <module>
LookupError: <ContextVar name='ctx' at 0x1021bbc70>
>>> exit()

It also got problem inside the functions when the context is referenced in global scope.

[iritkatriel]

3.9 is no longer maintained and I can't reproduce this on 3.10 and 3.11:

% python3.10 -m asyncio
asyncio REPL 3.10.4 (v3.10.4:9d38120e33, Mar 23 2022, 17:29:05) [Clang 13.0.0 (clang-1300.0.29.30)] on darwin
Use "await" directly instead of "asyncio.run()".
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> from contextvars import ContextVar
>>> ctx = ContextVar('ctx')
>>> ctx.set(1)
<Token var=<ContextVar name='ctx' at 0x10f704fe0> at 0x10f702000>
>>> 

I don't know what "other problems" you were seeing, but if you are still seeing them in 3.10+ please open reopen this or create a new issue with full details.

[wicol]

I'm getting the same thing with 3.11:

$ docker run --rm -it python:3.11-slim python -m asyncio
asyncio REPL 3.11.4 (main, Jun 14 2023, 18:43:41) [GCC 12.2.0] on linux
Use "await" directly instead of "asyncio.run()".
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> from contextvars import ContextVar
>>> ctx = ContextVar('ctx')
>>> ctx.set(1)
<Token var=<ContextVar name='ctx' at 0xffff900bb560> at 0xffff90051880>
>>> ctx.get()
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/concurrent/futures/_base.py", line 456, in result
    return self.__get_result()
           ^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/concurrent/futures/_base.py", line 401, in __get_result
    raise self._exception
  File "/usr/local/lib/python3.11/asyncio/__main__.py", line 34, in callback
    coro = func()
           ^^^^^^
  File "<console>", line 1, in <module>
LookupError: <ContextVar name='ctx' at 0xffff900bb560>
>>>

Oh and I'm on ARM (M1).

[terryjreedy]

Irit, you left off ctc.get(), which is what fails. I get same failure on Win10 local main compiled 10 hours ago.