Home Original page

bpo-44807: Allow Protocol classes to define __init__ by adriangb · Pull Request #31628 · python/cpython

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

bpo-44807: Allow Protocol classes to define __init__ #31628

Changes from all commits

Commits

File filter

Filter by extension

Conversations

Failed to load comments.

Loading

Jump to

Jump to file

Failed to load files.

Loading

Diff view
Diff view

26 changes: 26 additions & 0 deletions Lib/test/test_typing.py

Original file line number Diff line number Diff line change
Expand Up @@ -1074,6 +1074,32 @@ class CG(PG[T]): pass
with self.assertRaises(TypeError):
CG[int](42)

def test_protocol_defining_init_does_not_get_overridden(self):
# check that P.__init__ doesn't get clobbered
# see https://bugs.python.org/issue44807

class P(Protocol):
x: int
def __init__(self, x: int) -> None:
self.x = x
class C: pass

c = C()
P.__init__(c, 1)
self.assertEqual(c.x, 1)

def test_concrete_class_inheriting_init_from_protocol(self):
class P(Protocol):
x: int
def __init__(self, x: int) -> None:
self.x = x

class C(P): pass

c = C(1)
self.assertIsInstance(c, C)
self.assertEqual(c.x, 1)

def test_cannot_instantiate_abstract(self):
@runtime_checkable
class P(Protocol):
Expand Down

3 changes: 2 additions & 1 deletion Lib/typing.py

Original file line number Diff line number Diff line change
Expand Up @@ -1741,7 +1741,8 @@ def _proto_hook(other):
issubclass(base, Generic) and base._is_protocol):
raise TypeError('Protocols can only inherit from other'
' protocols, got %r' % base)
cls.__init__ = _no_init_or_replace_init
if cls.__init__ is Protocol.__init__:
cls.__init__ = _no_init_or_replace_init


class _AnnotatedAlias(_GenericAlias, _root=True):
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
:class:`typing.Protocol` no longer silently replaces :meth:`__init__` methods defined on subclasses. Patch by Adrian Garcia Badaracco.