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

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Merged
JelleZijlstra merged 7 commits into from
Apr 11, 2022
Merged

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

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e21200b
Allow Protocol classes to define __init__
adriangb Mar 1, 2022
fb419d1
📜🤖 Added by blurb_it.
blurb-it[bot] Mar 2, 2022
1fe020a
split up and improve test
adriangb Mar 2, 2022
9c22a44
Update Lib/test/test_typing.py
adriangb Mar 2, 2022
282e95f
Update Misc/NEWS.d/next/Library/2022-03-02-04-25-58.bpo-44807.gHNC9J.rst
adriangb Mar 2, 2022
28cf196
Update Lib/test/test_typing.py
adriangb Mar 2, 2022
e2840af
Update Lib/test/test_typing.py
JelleZijlstra Mar 10, 2022
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split up and improve test
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@adriangb
adriangb committed Mar 2, 2022
commit 1fe020aa4636ddfb466d072b21041407af0341e5
23 changes: 15 additions & 8 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1074,24 +1074,31 @@ class CG(PG[T]): pass
with self.assertRaises(TypeError):
CG[int](42)

def test_protocol_defining_init(self):
def test_protocol_defining_init_does_not_get_overriden(self):
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# 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

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class C: pass

# the protocol itself cannot be instantiated
with self.assertRaises(TypeError):
P()
c = C()
P.__init__(c, 1)
self.assertEqual(c.x, 1)

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

# but a concrete subclass can
class C(P): pass

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

# and this concrete subclass can inherit the __init__
# implementation from Protocol
self.assertEqual(c.x, 1)

def test_cannot_instantiate_abstract(self):
Expand Down