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| -rw-r--r-- | Doc/library/stdtypes.rst | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst index fdef531..0caa725 100644 --- a/Doc/library/stdtypes.rst +++ b/Doc/library/stdtypes.rst @@ -5162,6 +5162,14 @@ enables cleaner type hinting syntax compared to :data:`typing.Union`. def square(number: int | float) -> int | float: return number ** 2 + .. note:: + + The ``|`` operand cannot be used at runtime to define unions where one or + more members is a forward reference. For example, ``int | "Foo"``, where + ``"Foo"`` is a reference to a class not yet defined, will fail at + runtime. For unions which include forward references, present the + whole expression as a string, e.g. ``"int | Foo"``. + .. describe:: union_object == other Union objects can be tested for equality with other union objects. Details: |