pythongh-66944: Note that the contextlib.closing example is for ill…

…ustrative purposes (pythonGH-112198) (cherry picked from commit 9af9ac1) Co-authored-by: Ville Skyttä <[email protected]> Co-authored-by: Adam Turner <[email protected]>
miss-islington · Jan 23, 2024 · 9b1a9ff · 9b1a9ff
1 parent ed567c1
commit 9b1a9ff
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diff --git a/Doc/library/contextlib.rst b/Doc/library/contextlib.rst
@@ -182,6 +182,14 @@ Functions and classes provided:
    without needing to explicitly close ``page``.  Even if an error occurs,
    ``page.close()`` will be called when the :keyword:`with` block is exited.
 
+   .. note::
+
+      Most types managing resources support the :term:`context manager` protocol,
+      which closes *thing* on leaving the :keyword:`with` statment.
+      As such, :func:`!closing` is most useful for third party types that don't
+      support context managers.
+      This example is purely for illustration purposes,
+      as :func:`~urllib.request.urlopen` would normally be used in a context manager.
 
 .. function:: aclosing(thing)