Objects for Type Hinting — Python 3.10.17 documentation (original) (raw)

Various built-in types for type hinting are provided. Currently, two types exist – GenericAlias andUnion. Only GenericAlias is exposed to C.

PyObject *Py_GenericAlias(PyObject *origin, PyObject *args)¶

Part of the Stable ABI since version 3.9.

Create a GenericAlias object. Equivalent to calling the Python classtypes.GenericAlias. The origin and args arguments set theGenericAlias‘s __origin__ and __args__ attributes respectively.origin should be a [PyTypeObject](type.html#c.PyTypeObject "PyTypeObject")*, and args can be a[PyTupleObject](tuple.html#c.PyTupleObject "PyTupleObject")* or any PyObject*. If args passed is not a tuple, a 1-tuple is automatically constructed and __args__ is set to (args,). Minimal checking is done for the arguments, so the function will succeed even if origin is not a type. The GenericAlias‘s __parameters__ attribute is constructed lazily from __args__. On failure, an exception is raised and NULL is returned.

Here’s an example of how to make an extension type generic:

... static PyMethodDef my_obj_methods[] = { // Other methods. ... {"class_getitem", (PyCFunction)Py_GenericAlias, METH_O|METH_CLASS, "See PEP 585"} ... }