https://github.com/python/cpython/commit/94c8bac2cd50bd05aa1811d35f4b00f1080a40a9
commit: 94c8bac2cd50bd05aa1811d35f4b00f1080a40a9
branch: 3.15
author: Dino Viehland <[email protected]>
committer: DinoV <[email protected]>
date: 2026-05-18T17:53:54-07:00
summary:
[3.15] gh-148587: Make sys.lazy_modules match PEP and keep internal lazy
submodules tra… (#150014)
Make sys.lazy_modules match PEP and keep internal lazy submodules tracking
internal
files:
A Lib/test/test_lazy_import/__main__.py
A
Misc/NEWS.d/next/Core_and_Builtins/2026-05-18-18-36-28.gh-issue-148587.-RD3z5.rst
M Include/internal/pycore_interp_structs.h
M Lib/test/test_lazy_import/__init__.py
M Python/import.c
diff --git a/Include/internal/pycore_interp_structs.h
b/Include/internal/pycore_interp_structs.h
index f13bc2178b1e7e..d8e83cf2ff5c9a 100644
--- a/Include/internal/pycore_interp_structs.h
+++ b/Include/internal/pycore_interp_structs.h
@@ -349,7 +349,15 @@ struct _import_state {
int lazy_imports_mode;
PyObject *lazy_imports_filter;
PyObject *lazy_importing_modules;
+ // The set stored in sys.lazy_modules if values that have been
+ // lazily imported. This value is only for debugging/introspection
+ // purposes and is not used by the runtime.
PyObject *lazy_modules;
+ // A dict mapping package names to a set of submodule names that
+ // have been imported lazily from packages which have been imported
+ // lazily. When the package is reified we need to add a
+ // LazyImportObject which refers to the submodule on the module.
+ PyObject *lazy_pending_submodules;
#ifdef Py_GIL_DISABLED
PyMutex lazy_mutex;
#endif
diff --git a/Lib/test/test_lazy_import/__init__.py
b/Lib/test/test_lazy_import/__init__.py
index bcbf1a23233ba8..366cb203f8f256 100644
--- a/Lib/test/test_lazy_import/__init__.py
+++ b/Lib/test/test_lazy_import/__init__.py
@@ -38,8 +38,7 @@ def test_basic_unused(self):
"""Lazy imported module should not be loaded if never accessed."""
import test.test_lazy_import.data.basic_unused
self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
- self.assertIn("test.test_lazy_import.data", sys.lazy_modules)
- self.assertEqual(sys.lazy_modules["test.test_lazy_import.data"],
{"basic2"})
+ self.assertIn("test.test_lazy_import.data.basic2", sys.lazy_modules)
def test_sys_lazy_modules(self):
try:
@@ -49,7 +48,7 @@ def test_sys_lazy_modules(self):
self.assertFalse("test.test_lazy_import.data.basic2" in sys.modules)
self.assertIn("test.test_lazy_import.data", sys.lazy_modules)
- self.assertEqual(sys.lazy_modules["test.test_lazy_import.data"],
{"basic2"})
+ self.assertIn("test.test_lazy_import.data.basic2", sys.lazy_modules)
test.test_lazy_import.data.basic_from_unused.basic2
self.assertNotIn("test.test_import.data", sys.lazy_modules)
@@ -574,8 +573,8 @@ def my_filter(name):
self.assertIs(sys.get_lazy_imports_filter(), my_filter)
def test_lazy_modules_attribute_is_dict(self):
- """sys.lazy_modules should be a dict per PEP 810."""
- self.assertIsInstance(sys.lazy_modules, dict)
+ """sys.lazy_modules should be a set per PEP 810."""
+ self.assertIsInstance(sys.lazy_modules, set)
@support.requires_subprocess()
def test_lazy_modules_tracks_lazy_imports(self):
@@ -584,8 +583,7 @@ def test_lazy_modules_tracks_lazy_imports(self):
import sys
initial_count = len(sys.lazy_modules)
import test.test_lazy_import.data.basic_unused
- assert "test.test_lazy_import.data" in sys.lazy_modules
- assert sys.lazy_modules["test.test_lazy_import.data"] == {"basic2"}
+ assert "test.test_lazy_import.data.basic2" in sys.lazy_modules
assert len(sys.lazy_modules) > initial_count
print("OK")
""")
@@ -1034,15 +1032,14 @@ def
test_module_added_to_lazy_modules_on_lazy_import(self):
lazy import test.test_lazy_import.data.basic2
# Should be in lazy_modules after lazy import
- assert "test.test_lazy_import.data" in sys.lazy_modules
- assert sys.lazy_modules["test.test_lazy_import.data"] == {"basic2"}
+ assert "test.test_lazy_import.data.basic2" in sys.lazy_modules
assert len(sys.lazy_modules) > initial_count
# Trigger reification
_ = test.test_lazy_import.data.basic2.x
# Module should still be tracked (for diagnostics per PEP 810)
- assert "test.test_lazy_import.data" not in sys.lazy_modules
+ assert "test.test_lazy_import.data.basic2" not in sys.lazy_modules
print("OK")
""")
result = subprocess.run(
@@ -1055,8 +1052,8 @@ def
test_module_added_to_lazy_modules_on_lazy_import(self):
def test_lazy_modules_is_per_interpreter(self):
"""Each interpreter should have independent sys.lazy_modules."""
- # Basic test that sys.lazy_modules exists and is a dict
- self.assertIsInstance(sys.lazy_modules, dict)
+ # Basic test that sys.lazy_modules exists and is a set
+ self.assertIsInstance(sys.lazy_modules, set)
def test_lazy_module_without_children_is_tracked(self):
code = textwrap.dedent("""
@@ -1065,10 +1062,6 @@ def test_lazy_module_without_children_is_tracked(self):
assert "json" in sys.lazy_modules, (
f"expected 'json' in sys.lazy_modules, got
{set(sys.lazy_modules)}"
)
- assert sys.lazy_modules["json"] == set(), (
- f"expected empty set for sys.lazy_modules['json'], "
- f"got {sys.lazy_modules['json']!r}"
- )
print("OK")
""")
assert_python_ok("-c", code)
@@ -1937,7 +1930,7 @@ def create_lazy_imports(idx):
t.join()
assert not errors, f"Errors: {errors}"
- assert isinstance(sys.lazy_modules, dict), "sys.lazy_modules is
not a dict"
+ assert isinstance(sys.lazy_modules, set), "sys.lazy_modules is not
a dict"
print("OK")
""")
diff --git a/Lib/test/test_lazy_import/__main__.py
b/Lib/test/test_lazy_import/__main__.py
new file mode 100644
index 00000000000000..d6c94efaf30833
--- /dev/null
+++ b/Lib/test/test_lazy_import/__main__.py
@@ -0,0 +1,3 @@
+import unittest
+
+unittest.main('test.test_lazy_import')
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2026-05-18-18-36-28.gh-issue-148587.-RD3z5.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2026-05-18-18-36-28.gh-issue-148587.-RD3z5.rst
new file mode 100644
index 00000000000000..61bfdcdd37362c
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2026-05-18-18-36-28.gh-issue-148587.-RD3z5.rst
@@ -0,0 +1 @@
+``sys.lazy_modules`` is now a set instead of a dict as initially spelled out
in PEP 810.
diff --git a/Python/import.c b/Python/import.c
index 60a5ee6e770f59..c5cc7b52922d5b 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -94,6 +94,8 @@ static struct _inittab *inittab_copy = NULL;
(interp)->imports.modules_by_index
#define LAZY_MODULES(interp) \
(interp)->imports.lazy_modules
+#define LAZY_PENDING_SUBMODULES(interp) \
+ (interp)->imports.lazy_pending_submodules
#define IMPORTLIB(interp) \
(interp)->imports.importlib
#define OVERRIDE_MULTI_INTERP_EXTENSIONS_CHECK(interp) \
@@ -271,8 +273,11 @@ import_get_module(PyThreadState *tstate, PyObject *name)
PyObject *
_PyImport_InitLazyModules(PyInterpreterState *interp)
{
- assert(LAZY_MODULES(interp) == NULL);
- LAZY_MODULES(interp) = PyDict_New();
+ assert(LAZY_MODULES(interp) == NULL &&
+ LAZY_PENDING_SUBMODULES(interp) == NULL);
+
+ LAZY_PENDING_SUBMODULES(interp) = PyDict_New();
+ LAZY_MODULES(interp) = PySet_New(0);
return LAZY_MODULES(interp);
}
@@ -280,6 +285,7 @@ void
_PyImport_ClearLazyModules(PyInterpreterState *interp)
{
Py_CLEAR(LAZY_MODULES(interp));
+ Py_CLEAR(LAZY_PENDING_SUBMODULES(interp));
}
static int
@@ -4339,7 +4345,7 @@ get_mod_dict(PyObject *module)
// ensure we have the set for the parent module name in sys.lazy_modules.
// Returns a new reference.
static PyObject *
-ensure_lazy_submodules(PyDictObject *lazy_modules, PyObject *parent)
+ensure_lazy_pending_submodules(PyDictObject *lazy_modules, PyObject *parent)
{
PyObject *lazy_submodules;
Py_BEGIN_CRITICAL_SECTION(lazy_modules);
@@ -4358,6 +4364,9 @@ ensure_lazy_submodules(PyDictObject *lazy_modules,
PyObject *parent)
return lazy_submodules;
}
+// Ensures that we have a LazyImportObject on the parent module for
+// all children modules which have been lazily imported. If the parent
+// module overrides the child attribute then the value is not replaced.
static int
register_lazy_on_parent(PyThreadState *tstate, PyObject *name,
PyObject *builtins)
@@ -4369,16 +4378,16 @@ register_lazy_on_parent(PyThreadState *tstate, PyObject
*name,
PyObject *parent_dict = NULL;
PyInterpreterState *interp = tstate->interp;
- PyObject *lazy_modules = LAZY_MODULES(interp);
- assert(lazy_modules != NULL);
+ PyObject *lazy_pending_submodules = LAZY_PENDING_SUBMODULES(interp);
+ assert(lazy_pending_submodules != NULL);
Py_INCREF(name);
while (true) {
Py_ssize_t dot = PyUnicode_FindChar(name, '.', 0,
PyUnicode_GET_LENGTH(name), -1);
if (dot < 0) {
- PyObject *lazy_submodules = ensure_lazy_submodules(
- (PyDictObject *)lazy_modules, name);
+ PyObject *lazy_submodules = ensure_lazy_pending_submodules(
+ (PyDictObject *)lazy_pending_submodules, name);
if (lazy_submodules == NULL) {
goto done;
}
@@ -4400,8 +4409,8 @@ register_lazy_on_parent(PyThreadState *tstate, PyObject
*name,
}
// Record the child as being lazily imported from the parent.
- PyObject *lazy_submodules = ensure_lazy_submodules(
- (PyDictObject *)lazy_modules, parent);
+ PyObject *lazy_submodules = ensure_lazy_pending_submodules(
+ (PyDictObject *)lazy_pending_submodules, parent);
if (lazy_submodules == NULL) {
goto done;
}
@@ -4464,6 +4473,14 @@ register_from_lazy_on_parent(PyThreadState *tstate,
PyObject *abs_name,
if (fromname == NULL) {
return -1;
}
+
+ // Add the module name to sys.lazy_modules set (PEP 810).
+ PyObject *lazy_modules = LAZY_MODULES(tstate->interp);
+ if (PySet_Add(lazy_modules, fromname) < 0) {
+ Py_DECREF(fromname);
+ return -1;
+ }
+
int res = register_lazy_on_parent(tstate, fromname, builtins);
Py_DECREF(fromname);
return res;
@@ -4555,6 +4572,13 @@ _PyImport_LazyImportModuleLevelObject(PyThreadState
*tstate,
Py_DECREF(abs_name);
return NULL;
}
+
+ // Add the module name to sys.lazy_modules set (PEP 810).
+ PyObject *lazy_modules = LAZY_MODULES(tstate->interp);
+ if (PySet_Add(lazy_modules, abs_name) < 0) {
+ goto error;
+ }
+
if (fromlist && PyUnicode_Check(fromlist)) {
if (register_from_lazy_on_parent(tstate, abs_name, fromlist,
builtins) < 0) {
@@ -4791,6 +4815,7 @@ _PyImport_ClearCore(PyInterpreterState *interp)
Py_CLEAR(IMPORTLIB(interp));
Py_CLEAR(IMPORT_FUNC(interp));
Py_CLEAR(LAZY_IMPORT_FUNC(interp));
+ Py_CLEAR(interp->imports.lazy_pending_submodules);
Py_CLEAR(interp->imports.lazy_modules);
Py_CLEAR(interp->imports.lazy_importing_modules);
Py_CLEAR(interp->imports.lazy_imports_filter);
@@ -5636,11 +5661,13 @@ _imp__set_lazy_attributes_impl(PyObject *module,
PyObject *modobj,
PyThreadState *tstate = _PyThreadState_GET();
PyObject *module_dict = NULL;
PyObject *ret = NULL;
- PyObject *lazy_modules = LAZY_MODULES(tstate->interp);
- assert(lazy_modules != NULL);
+ PyObject *lazy_pending_modules = LAZY_PENDING_SUBMODULES(tstate->interp);
+ assert(lazy_pending_modules != NULL);
PyObject *lazy_submodules;
- if (PyDict_GetItemRef(lazy_modules, name, &lazy_submodules) < 0) {
+ if (PySet_Discard(LAZY_MODULES(tstate->interp), name) < 0) {
+ return NULL;
+ } else if (PyDict_GetItemRef(lazy_pending_modules, name, &lazy_submodules)
< 0) {
return NULL;
}
else if (lazy_submodules == NULL) {
@@ -5659,8 +5686,7 @@ _imp__set_lazy_attributes_impl(PyObject *module, PyObject
*modobj,
Py_END_CRITICAL_SECTION();
Py_DECREF(lazy_submodules);
- // once a module is imported it is removed from sys.lazy_modules
- if (PyDict_DelItem(lazy_modules, name) < 0) {
+ if (PyDict_DelItem(lazy_pending_modules, name) < 0) {
goto error;
}
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