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[3.8] bpo-44018: random.seed() no longer mutates its inputs (GH-25856) #25865

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[3.8] bpo-44018: random.seed() no longer mutates its inputs (GH-25856) #25865

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3 changes: 1 addition & 2 deletions Lib/random.py
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Original file line number Diff line number Diff line change
Expand Up @@ -146,8 +146,7 @@ def seed(self, a=None, version=2):
if version == 2 and isinstance(a, (str, bytes, bytearray)):
if isinstance(a, str):
a = a.encode()
a += _sha512(a).digest()
a = int.from_bytes(a, 'big')
a = int.from_bytes(a + _sha512(a).digest(), 'big')

super().seed(a)
self.gauss_next = None
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5 changes: 5 additions & 0 deletions Lib/test/test_random.py
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Expand Up @@ -49,6 +49,11 @@ def __hash__(self):
self.assertRaises(TypeError, self.gen.seed, 1, 2, 3, 4)
self.assertRaises(TypeError, type(self.gen), [])

def test_seed_no_mutate_bug_44018(self):
a = bytearray(b'1234')
self.gen.seed(a)
self.assertEqual(a, bytearray(b'1234'))

@unittest.mock.patch('random._urandom') # os.urandom
def test_seed_when_randomness_source_not_found(self, urandom_mock):
# Random.seed() uses time.time() when an operating system specific
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2021-05-03-10-07-43.bpo-44018.VDyW8f.rst
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@@ -0,0 +1 @@
random.seed() no longer mutates bytearray inputs.