.. _consider-alternative-union-syntax:

consider-alternative-union-syntax / R6003
=========================================

**Message emitted:**

``Consider using alternative union syntax instead of '%s'%s``

**Description:**

*Emitted when ``typing.Union`` or ``typing.Optional`` is used instead of the shorthand union syntax. For example, ``Union[int, float]`` instead of ``int | float``. Using the shorthand for unions aligns with Python typing recommendations, removes the need for imports, and avoids confusion in function signatures.*

**Problematic code:**

.. literalinclude:: /data/messages/c/consider-alternative-union-syntax/bad.py
   :language: python

**Correct code:**

.. literalinclude:: /data/messages/c/consider-alternative-union-syntax/good.py
   :language: python

**Configuration file:**

.. literalinclude:: /data/messages/c/consider-alternative-union-syntax/pylintrc
    :language: ini

**Additional details:**

Using the shorthand syntax for union types is |recommended over the typing module|__. This is consistent with the broader recommendation to prefer built-in types over imports (for example, using ``list`` instead of the now-deprecated ``typing.List``).

``typing.Optional`` can also cause confusion in annotated function arguments, since an argument annotated as ``Optional`` is still a *required* argument when a default value is not set. Explicitly annotating such arguments with ``type | None`` makes the intention clear.

.. |recommended over the typing module| replace:: recommended over the ``typing`` module
__ https://docs.python.org/3/library/typing.html#typing.Union




.. note::
  This message is emitted by the optional :ref:`'typing'<pylint.extensions.typing>`
  checker, which requires the ``pylint.extensions.typing`` plugin to be loaded.

Created by the `typing <https://github.com/pylint-dev/pylint/blob/main/pylint/extensions/typing.py>`__ checker.