https://github.com/python/cpython/commit/a65611e7f52dae341915e79eb28c47aec930f077
commit: a65611e7f52dae341915e79eb28c47aec930f077
branch: main
author: Eric Mark Martin <[email protected]>
committer: JelleZijlstra <[email protected]>
date: 2026-05-02T17:28:08Z
summary:
gh-149171: Make TypeAliasType __module__ writable (#149172)
closes #149171.
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2026-04-30-01-35-09.gh-issue-149171.meXWpl.rst
M Doc/library/typing.rst
M Lib/test/test_type_aliases.py
M Objects/typevarobject.c
diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst
index 1957cadcbb1592..17cf57dd00b4bd 100644
--- a/Doc/library/typing.rst
+++ b/Doc/library/typing.rst
@@ -2361,6 +2361,12 @@ without the dedicated syntax, as documented below.
>>> Alias.__module__
'__main__'
+ This attribute is writable.
+
+ .. versionchanged:: 3.15
+
+ The attribute is now writable.
+
.. attribute:: __type_params__
The type parameters of the type alias, or an empty tuple if the alias is
diff --git a/Lib/test/test_type_aliases.py b/Lib/test/test_type_aliases.py
index 9ceee565764c9a..05bc6a80888a06 100644
--- a/Lib/test/test_type_aliases.py
+++ b/Lib/test/test_type_aliases.py
@@ -372,6 +372,8 @@ def test_module(self):
mod_generics_cache.__name__)
self.assertEqual(mod_generics_cache.OldStyle.__module__,
mod_generics_cache.__name__)
+ Alias.__module__ = "ham.spam.eggs"
+ self.assertEqual(Alias.__module__, "ham.spam.eggs")
def test_unpack(self):
type Alias = tuple[int, int]
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2026-04-30-01-35-09.gh-issue-149171.meXWpl.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-30-01-35-09.gh-issue-149171.meXWpl.rst
new file mode 100644
index 00000000000000..f8320dd4c6b3c2
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-30-01-35-09.gh-issue-149171.meXWpl.rst
@@ -0,0 +1,2 @@
+Allow assignment to the ``__module__`` attribute of
+:class:`typing.TypeAliasType` instances.
diff --git a/Objects/typevarobject.c b/Objects/typevarobject.c
index cdc0ea42eac263..8ad590cc6e6093 100644
--- a/Objects/typevarobject.c
+++ b/Objects/typevarobject.c
@@ -1983,8 +1983,12 @@ static PyObject *
typealias_module(PyObject *self, void *Py_UNUSED(closure))
{
typealiasobject *ta = typealiasobject_CAST(self);
- if (ta->module != NULL) {
- return Py_NewRef(ta->module);
+ PyObject *module;
+ Py_BEGIN_CRITICAL_SECTION(self);
+ module = Py_XNewRef(ta->module);
+ Py_END_CRITICAL_SECTION();
+ if (module != NULL) {
+ return module;
}
if (ta->compute_value != NULL) {
PyObject* mod = PyFunction_GetModule(ta->compute_value);
@@ -1998,12 +2002,25 @@ typealias_module(PyObject *self, void
*Py_UNUSED(closure))
Py_RETURN_NONE;
}
+static int
+typealias_set_module(PyObject *self, PyObject *value, void *Py_UNUSED(closure))
+{
+ PyObject *old;
+ typealiasobject *ta = typealiasobject_CAST(self);
+ Py_BEGIN_CRITICAL_SECTION(self);
+ old = ta->module;
+ ta->module = Py_XNewRef(value);
+ Py_END_CRITICAL_SECTION();
+ Py_XDECREF(old);
+ return 0;
+}
+
static PyGetSetDef typealias_getset[] = {
{"__parameters__", typealias_parameters, NULL, NULL, NULL},
{"__type_params__", typealias_type_params, NULL, NULL, NULL},
{"__value__", typealias_value, NULL, NULL, NULL},
{"evaluate_value", typealias_evaluate_value, NULL, NULL, NULL},
- {"__module__", typealias_module, NULL, NULL, NULL},
+ {"__module__", typealias_module, typealias_set_module, NULL, NULL},
{0}
};
@@ -2203,7 +2220,9 @@ type checkers.\n\
At runtime, Alias is an instance of TypeAliasType. The __name__\n\
attribute holds the name of the type alias. The value of the type alias\n\
is stored in the __value__ attribute. It is evaluated lazily, so the\n\
-value is computed only if the attribute is accessed.\n\
+value is computed only if the attribute is accessed. The __module__\n\
+attribute holds the name of the module in which the type alias was\n\
+defined; it can be assigned to.\n\
\n\
Type aliases can also be generic::\n\
\n\
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