cpython/Doc/deprecations/pending-removal-in-3.17.rst

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Pending removal in Python 3.17
------------------------------
* :mod:`collections.abc`:
- :class:`collections.abc.ByteString` is scheduled for removal in Python 3.17.
Use ``isinstance(obj, collections.abc.Buffer)`` to test if ``obj``
implements the :ref:`buffer protocol <bufferobjects>` at runtime. For use
in type annotations, either use :class:`~collections.abc.Buffer` or a union
that explicitly specifies the types your code supports (e.g.,
``bytes | bytearray | memoryview``).
:class:`!ByteString` was originally intended to be an abstract class that
would serve as a supertype of both :class:`bytes` and :class:`bytearray`.
However, since the ABC never had any methods, knowing that an object was an
instance of :class:`!ByteString` never actually told you anything useful
about the object. Other common buffer types such as :class:`memoryview`
were also never understood as subtypes of :class:`!ByteString` (either at
runtime or by static type checkers).
See :pep:`PEP 688 <688#current-options>` for more details.
(Contributed by Shantanu Jain in :gh:`91896`.)
* :mod:`typing`:
- Before Python 3.14, old-style unions were implemented using the private class
``typing._UnionGenericAlias``. This class is no longer needed for the implementation,
but it has been retained for backward compatibility, with removal scheduled for Python
3.17. Users should use documented introspection helpers like :func:`typing.get_origin`
and :func:`typing.get_args` instead of relying on private implementation details.
- :class:`typing.ByteString`, deprecated since Python 3.9, is scheduled for removal in
Python 3.17.
Use ``isinstance(obj, collections.abc.Buffer)`` to test if ``obj``
implements the :ref:`buffer protocol <bufferobjects>` at runtime. For use
in type annotations, either use :class:`~collections.abc.Buffer` or a union
that explicitly specifies the types your code supports (e.g.,
``bytes | bytearray | memoryview``).
:class:`!ByteString` was originally intended to be an abstract class that
would serve as a supertype of both :class:`bytes` and :class:`bytearray`.
However, since the ABC never had any methods, knowing that an object was an
instance of :class:`!ByteString` never actually told you anything useful
about the object. Other common buffer types such as :class:`memoryview`
were also never understood as subtypes of :class:`!ByteString` (either at
runtime or by static type checkers).
See :pep:`PEP 688 <688#current-options>` for more details.
(Contributed by Shantanu Jain in :gh:`91896`.)