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gh-148587: Make sys.lazy_modules immutable #149408

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351473b
gh-148587: Make sys.lazy_modules an immutable frozendict snapshot
johnslavik Apr 26, 2026
083bbe9
gh-148587: Expose live lazy import registry as sys._lazy_modules
johnslavik May 4, 2026
eac60ed
gh-148587: Address review feedback on sys.lazy_modules
johnslavik May 5, 2026
0424a64
gh-148587: Trim sys.lazy_modules contract test and NEWS
johnslavik May 5, 2026
4404972
gh-148587: Align sys.__getattr__ with _ctypes/zlib pattern
johnslavik May 5, 2026
f4f8fb2
gh-148587: Use METH_VARARGS for sys.__getattr__
johnslavik May 5, 2026
a94f4e7
gh-148587: Pre-size and short-circuit empty in lazy modules snapshot
johnslavik May 5, 2026
926a02e
Revert pre-size and empty fast path in lazy modules snapshot
johnslavik May 5, 2026
ca32d07
Add docstring to sys.__getattr__
johnslavik May 5, 2026
3dff9ef
Add sys.__dir__ so lazy_modules appears in tab completion
johnslavik May 5, 2026
2c0e3f2
Fix METH_NOARGS signature and wrap long line in sys_dir/sys_getattr
johnslavik May 5, 2026
17de69e
Add sys.lazy_modules docs and fix CI test failures
johnslavik May 5, 2026
46c6033
Remove internal _lazy_modules mention and bogus set_lazy_imports cros…
johnslavik May 5, 2026
e4bbea8
Fix test_sys_module_has_signatures: METH_NOARGS never has None text s…
johnslavik May 17, 2026
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gh-148587: Trim sys.lazy_modules contract test and NEWS 
Drop test_lazy_modules_is_immutable; the frozendict assertion already
covers immutability. Trim the trailing sentence in the NEWS entry that
restated the same contract.
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johnslavik committed May 5, 2026
commit 0424a64806a0eb2c2ed31a85d7faf204dd4c6401
8 changes: 0 additions & 8 deletions Lib/test/test_lazy_import/__init__.py
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Expand Up @@ -499,14 +499,6 @@ def test_lazy_modules_returns_fresh_mapping(self):
self.assertIsNot(first, second)
self.assertEqual(first, second)

def test_lazy_modules_is_immutable(self):
"""Mutation through sys.lazy_modules must not be possible."""
snapshot = sys.lazy_modules
with self.assertRaises(TypeError):
snapshot["foo"] = frozenset()
with self.assertRaises(AttributeError):
snapshot.clear()

def test_underscore_lazy_modules_is_live_dict(self):
"""sys._lazy_modules should be the live, mutable registry."""
registry = sys._lazy_modules
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3 changes: 1 addition & 2 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-04-26-20-44-58.gh-issue-148587.f791BR.rst
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@@ -1,5 +1,4 @@
:data:`sys.lazy_modules` is now a read-only :class:`frozendict` mapping
each module's fully qualified name to the :class:`frozenset` of its
lazily-imported submodule names, instead of a live mutable :class:`dict`
of :class:`set` objects. User code can no longer mutate the lazy import
registry through this attribute.
of :class:`set` objects.