bpo-33144: Fix choosing random.Random._randbelow implementation. (GH-6563)
random() takes precedence over getrandbits() if defined later in the class tree.
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@ -102,18 +102,16 @@ class Random(_random.Random):
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ranges.
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"""
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if (cls.random is _random.Random.random) or (
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cls.getrandbits is not _random.Random.getrandbits):
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# The original random() builtin method has not been overridden
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# or a new getrandbits() was supplied.
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# The subclass can use the getrandbits-dependent implementation
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# of _randbelow().
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cls._randbelow = cls._randbelow_with_getrandbits
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else:
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# There's an overridden random() method but no new getrandbits(),
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# so the subclass can only use the getrandbits-independent
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# implementation of _randbelow().
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cls._randbelow = cls._randbelow_without_getrandbits
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for c in cls.__mro__:
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if '_randbelow' in c.__dict__:
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# just inherit it
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break
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if 'getrandbits' in c.__dict__:
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cls._randbelow = cls._randbelow_with_getrandbits
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break
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if 'random' in c.__dict__:
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cls._randbelow = cls._randbelow_without_getrandbits
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break
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def seed(self, a=None, version=2):
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"""Initialize internal state from hashable object.
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@ -5,7 +5,6 @@ import os
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import time
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import pickle
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import warnings
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import logging
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from functools import partial
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from math import log, exp, pi, fsum, sin, factorial
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from test import support
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@ -940,6 +939,7 @@ class TestDistributions(unittest.TestCase):
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gammavariate_mock.return_value = 0.0
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self.assertEqual(0.0, random.betavariate(2.71828, 3.14159))
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class TestRandomSubclassing(unittest.TestCase):
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def test_random_subclass_with_kwargs(self):
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# SF bug #1486663 -- this used to erroneously raise a TypeError
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@ -958,30 +958,80 @@ class TestRandomSubclassing(unittest.TestCase):
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# randrange
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class SubClass1(random.Random):
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def random(self):
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return super().random()
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called.add('SubClass1.random')
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return random.Random.random(self)
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def getrandbits(self, n):
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logging.getLogger('getrandbits').info('used getrandbits')
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return super().getrandbits(n)
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with self.assertLogs('getrandbits'):
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SubClass1().randrange(42)
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called.add('SubClass1.getrandbits')
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return random.Random.getrandbits(self, n)
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called = set()
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SubClass1().randrange(42)
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self.assertEqual(called, {'SubClass1.getrandbits'})
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# subclass providing only random => can only use random for randrange
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class SubClass2(random.Random):
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def random(self):
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logging.getLogger('random').info('used random')
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return super().random()
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with self.assertLogs('random'):
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SubClass2().randrange(42)
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called.add('SubClass2.random')
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return random.Random.random(self)
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called = set()
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SubClass2().randrange(42)
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self.assertEqual(called, {'SubClass2.random'})
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# subclass defining getrandbits to complement its inherited random
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# => can now rely on getrandbits for randrange again
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class SubClass3(SubClass2):
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def getrandbits(self, n):
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logging.getLogger('getrandbits').info('used getrandbits')
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return super().getrandbits(n)
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with self.assertLogs('getrandbits'):
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SubClass3().randrange(42)
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called.add('SubClass3.getrandbits')
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return random.Random.getrandbits(self, n)
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called = set()
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SubClass3().randrange(42)
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self.assertEqual(called, {'SubClass3.getrandbits'})
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# subclass providing only random and inherited getrandbits
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# => random takes precedence
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class SubClass4(SubClass3):
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def random(self):
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called.add('SubClass4.random')
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return random.Random.random(self)
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called = set()
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SubClass4().randrange(42)
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self.assertEqual(called, {'SubClass4.random'})
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# Following subclasses don't define random or getrandbits directly,
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# but inherit them from classes which are not subclasses of Random
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class Mixin1:
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def random(self):
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called.add('Mixin1.random')
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return random.Random.random(self)
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class Mixin2:
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def getrandbits(self, n):
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called.add('Mixin2.getrandbits')
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return random.Random.getrandbits(self, n)
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class SubClass5(Mixin1, random.Random):
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pass
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called = set()
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SubClass5().randrange(42)
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self.assertEqual(called, {'Mixin1.random'})
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class SubClass6(Mixin2, random.Random):
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pass
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called = set()
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SubClass6().randrange(42)
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self.assertEqual(called, {'Mixin2.getrandbits'})
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class SubClass7(Mixin1, Mixin2, random.Random):
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pass
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called = set()
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SubClass7().randrange(42)
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self.assertEqual(called, {'Mixin1.random'})
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class SubClass8(Mixin2, Mixin1, random.Random):
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pass
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called = set()
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SubClass8().randrange(42)
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self.assertEqual(called, {'Mixin2.getrandbits'})
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class TestModule(unittest.TestCase):
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def testMagicConstants(self):
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