https://github.com/python/cpython/commit/76bdeebef6c6206f3e0af1e42cbfc75c51fbb8ca commit: 76bdeebef6c6206f3e0af1e42cbfc75c51fbb8ca branch: main author: Bénédikt Tran <10796600+picn...@users.noreply.github.com> committer: AA-Turner <9087854+aa-tur...@users.noreply.github.com> date: 2024-08-07T13:40:19Z summary:
gh-122511: Improve documentation for object identity of mutable/immutable types (#122512) Co-authored-by: Adam Turner <9087854+aa-tur...@users.noreply.github.com> files: M Doc/reference/datamodel.rst diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index aa61fbdd3131f6..f099d5553963e0 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -106,12 +106,16 @@ that mutable object is changed. Types affect almost all aspects of object behavior. Even the importance of object identity is affected in some sense: for immutable types, operations that compute new values may actually return a reference to any existing object with -the same type and value, while for mutable objects this is not allowed. E.g., -after ``a = 1; b = 1``, ``a`` and ``b`` may or may not refer to the same object -with the value one, depending on the implementation, but after ``c = []; d = -[]``, ``c`` and ``d`` are guaranteed to refer to two different, unique, newly -created empty lists. (Note that ``c = d = []`` assigns the same object to both -``c`` and ``d``.) +the same type and value, while for mutable objects this is not allowed. +For example, after ``a = 1; b = 1``, *a* and *b* may or may not refer to +the same object with the value one, depending on the implementation. +This is because :class:`int` is an immutable type, so the reference to ``1`` +can be reused. This behaviour depends on the implementation used, so should +not be relied upon, but is something to be aware of when making use of object +identity tests. +However, after ``c = []; d = []``, *c* and *d* are guaranteed to refer to two +different, unique, newly created empty lists. (Note that ``e = f = []`` assigns +the *same* object to both *e* and *f*.) .. _types: _______________________________________________ Python-checkins mailing list -- python-checkins@python.org To unsubscribe send an email to python-checkins-le...@python.org https://mail.python.org/mailman3/lists/python-checkins.python.org/ Member address: arch...@mail-archive.com
