Fix typo in multiprocessing.pool.AsyncResult.successful doc.

[awecx]

Since 3.7 successful raises a ValueError as explained in the next text block from the documentation:

Changed in version 3.7: If the result is not ready, ValueError is raised instead of AssertionError.

No issue associated with this PR.
Should be backported in 3.7 and 3.8.

Automerge-Triggered-By: @pitrou

[aeros]

Thanks for the PR @awecx.

I confirmed from the source code that AsyncResult.successful() does indeed raise a ValueError instead of an AssertionError:

cpython/Lib/multiprocessing/pool.py

Lines 753 to 756 in a796d8e

	def successful(self):
	if not self.ready():
	raise ValueError("{0!r} not ready".format(self))
	return self._success

LGTM. This is also present in the 3.8 and 3.7 branches, so this PR should be backported to those versions as well.

[aeros]

Added @pitrou as a reviewer for the PR, since he's an active expert for the multiprocessing module.

[awecx]

Thanks for the PR @awecx.

I confirmed from the source code that AsyncResult.successful() does indeed raise a ValueError instead of an AssertionError:

cpython/Lib/multiprocessing/pool.py

Lines 753 to 756 in a796d8e

	def successful(self):
	if not self.ready():
	raise ValueError("{0!r} not ready".format(self))
	return self._success

LGTM. This is also present in the 3.8 and 3.7 branches, so this PR should be backported to those versions as well.

Thanks @aeros for the clarification. Indeed I should have proven the typo claim more clearly:
@pitrou if double check is necessary, you can run the following snippet:

from multiprocessing import Pool
from time import sleep

with Pool(processes=1) as pool:
    result = pool.apply_async(sleep, (10000,))
    result.successful()

[pitrou]

+1

[miss-islington]

Thanks @awecx for the PR 🌮🎉.. I'm working now to backport this PR to: 3.7, 3.8.
🐍🍒⛏🤖

[bedevere-bot]

GH-18015 is a backport of this pull request to the 3.8 branch.

[bedevere-bot]

GH-18016 is a backport of this pull request to the 3.7 branch.