Skip to content

gh-134537: Clarify context manager reuse in ContextDecorator #159848

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
limadog9 wants to merge 1 commit into
base: main
Choose a base branch
from
+13 −7
Open

gh-134537: Clarify context manager reuse in ContextDecorator #159848

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
20 changes: 13 additions & 7 deletions Doc/library/contextlib.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -434,17 +434,18 @@ Functions and classes provided:
The bit in the middle
Finishing

This change is just syntactic sugar for any construct of the following form::
The decorator form is::

@cm()
def f():
with cm():
# Do stuff
# Do stuff

``ContextDecorator`` lets you instead write::
By default, this reuses a single context manager instance, as in::

@cm()
context = cm()
def f():
# Do stuff
with context:
# Do stuff

It makes it clear that the ``cm`` applies to the whole function, rather than
just a piece of it (and saving an indentation level is nice, too).
Expand All @@ -465,7 +466,12 @@ Functions and classes provided:
As the decorated function must be able to be called multiple times, the
underlying context manager must support use in multiple :keyword:`with`
statements. If this is not the case, then the original construct with the
explicit :keyword:`!with` statement inside the function should be used.
explicit :keyword:`!with` statement and a new context manager inside the
function should be used.

Recursive calls require the context manager to support nested use, and
concurrent calls require it to be thread-safe. Context managers created
by :deco:`contextmanager` are recreated for each call, as described above.

When the decorated callable is a generator function, coroutine function, or
asynchronous generator function, the returned wrapper is of the same kind
Expand Down
Loading