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Add TYPE_CHECKING builtin #131793

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Add TYPE_CHECKING builtin #131793

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793b036
Add TYPE_CHECKING builtin
methane Mar 27, 2025
73412a8
Add doc
methane Mar 27, 2025
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9 changes: 9 additions & 0 deletions Doc/library/constants.rst
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Expand Up @@ -70,6 +70,15 @@ A small number of constants live in the built-in namespace. They are:
``Ellipsis`` is the sole instance of the :data:`types.EllipsisType` type.


.. data:: TYPE_CHECKING

This constant is same to :data:`typing.TYPE_CHECKING`.
It is always ``False`` at runtime, but third party static type checkers
assumes it to be ``True``.

.. versionadded:: next


.. data:: __debug__

This constant is true if Python was not started with an :option:`-O` option.
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1 change: 1 addition & 0 deletions Python/bltinmodule.c
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Expand Up @@ -3407,6 +3407,7 @@ _PyBuiltin_Init(PyInterpreterState *interp)
SETBUILTIN("tuple", &PyTuple_Type);
SETBUILTIN("type", &PyType_Type);
SETBUILTIN("zip", &PyZip_Type);
SETBUILTIN("TYPE_CHECKING", Py_False);
debug = PyBool_FromLong(config->optimization_level == 0);
if (PyDict_SetItemString(dict, "__debug__", debug) < 0) {
Py_DECREF(debug);
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