[Python-checkins] bpo-33144: Fix choosing random.Random._randbelow implementation. (GH-6563)

Tue May 8 08:45:20 EDT 2018

https://github.com/python/cpython/commit/ec1622d56c80d15740f7f8459c9a79fd55f5d3c7
commit: ec1622d56c80d15740f7f8459c9a79fd55f5d3c7
branch: master
author: Serhiy Storchaka <storchaka at gmail.com>
committer: GitHub <noreply at github.com>
date: 2018年05月08日T15:45:15+03:00
summary:
bpo-33144: Fix choosing random.Random._randbelow implementation. (GH-6563)
random() takes precedence over getrandbits() if defined later
in the class tree.
files:
M Lib/random.py
M Lib/test/test_random.py

diff --git a/Lib/random.py b/Lib/random.py
index 0ed5511e9f63..1e0dcc87ed4a 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -102,18 +102,16 @@ def __init_subclass__(cls, **kwargs):
 ranges.
 """
 
- if (cls.random is _random.Random.random) or (
- cls.getrandbits is not _random.Random.getrandbits):
- # The original random() builtin method has not been overridden
- # or a new getrandbits() was supplied.
- # The subclass can use the getrandbits-dependent implementation
- # of _randbelow().
- cls._randbelow = cls._randbelow_with_getrandbits
- else:
- # There's an overridden random() method but no new getrandbits(),
- # so the subclass can only use the getrandbits-independent
- # implementation of _randbelow().
- cls._randbelow = cls._randbelow_without_getrandbits
+ for c in cls.__mro__:
+ if '_randbelow' in c.__dict__:
+ # just inherit it
+ break
+ if 'getrandbits' in c.__dict__:
+ cls._randbelow = cls._randbelow_with_getrandbits
+ break
+ if 'random' in c.__dict__:
+ cls._randbelow = cls._randbelow_without_getrandbits
+ break
 
 def seed(self, a=None, version=2):
 """Initialize internal state from hashable object.
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
index d91908b03d02..e7ef68ba3d26 100644
--- a/Lib/test/test_random.py
+++ b/Lib/test/test_random.py
@@ -5,7 +5,6 @@
 import time
 import pickle
 import warnings
-import logging
 from functools import partial
 from math import log, exp, pi, fsum, sin, factorial
 from test import support
@@ -940,6 +939,7 @@ def test_betavariate_return_zero(self, gammavariate_mock):
 gammavariate_mock.return_value = 0.0
 self.assertEqual(0.0, random.betavariate(2.71828, 3.14159))
 
+
 class TestRandomSubclassing(unittest.TestCase):
 def test_random_subclass_with_kwargs(self):
 # SF bug #1486663 -- this used to erroneously raise a TypeError
@@ -958,30 +958,80 @@ def test_subclasses_overriding_methods(self):
 # randrange
 class SubClass1(random.Random):
 def random(self):
- return super().random()
+ called.add('SubClass1.random')
+ return random.Random.random(self)
 
 def getrandbits(self, n):
- logging.getLogger('getrandbits').info('used getrandbits')
- return super().getrandbits(n)
- with self.assertLogs('getrandbits'):
- SubClass1().randrange(42)
+ called.add('SubClass1.getrandbits')
+ return random.Random.getrandbits(self, n)
+ called = set()
+ SubClass1().randrange(42)
+ self.assertEqual(called, {'SubClass1.getrandbits'})
 
 # subclass providing only random => can only use random for randrange
 class SubClass2(random.Random):
 def random(self):
- logging.getLogger('random').info('used random')
- return super().random()
- with self.assertLogs('random'):
- SubClass2().randrange(42)
+ called.add('SubClass2.random')
+ return random.Random.random(self)
+ called = set()
+ SubClass2().randrange(42)
+ self.assertEqual(called, {'SubClass2.random'})
 
 # subclass defining getrandbits to complement its inherited random
 # => can now rely on getrandbits for randrange again
 class SubClass3(SubClass2):
 def getrandbits(self, n):
- logging.getLogger('getrandbits').info('used getrandbits')
- return super().getrandbits(n)
- with self.assertLogs('getrandbits'):
- SubClass3().randrange(42)
+ called.add('SubClass3.getrandbits')
+ return random.Random.getrandbits(self, n)
+ called = set()
+ SubClass3().randrange(42)
+ self.assertEqual(called, {'SubClass3.getrandbits'})
+
+ # subclass providing only random and inherited getrandbits
+ # => random takes precedence
+ class SubClass4(SubClass3):
+ def random(self):
+ called.add('SubClass4.random')
+ return random.Random.random(self)
+ called = set()
+ SubClass4().randrange(42)
+ self.assertEqual(called, {'SubClass4.random'})
+
+ # Following subclasses don't define random or getrandbits directly,
+ # but inherit them from classes which are not subclasses of Random
+ class Mixin1:
+ def random(self):
+ called.add('Mixin1.random')
+ return random.Random.random(self)
+ class Mixin2:
+ def getrandbits(self, n):
+ called.add('Mixin2.getrandbits')
+ return random.Random.getrandbits(self, n)
+
+ class SubClass5(Mixin1, random.Random):
+ pass
+ called = set()
+ SubClass5().randrange(42)
+ self.assertEqual(called, {'Mixin1.random'})
+
+ class SubClass6(Mixin2, random.Random):
+ pass
+ called = set()
+ SubClass6().randrange(42)
+ self.assertEqual(called, {'Mixin2.getrandbits'})
+
+ class SubClass7(Mixin1, Mixin2, random.Random):
+ pass
+ called = set()
+ SubClass7().randrange(42)
+ self.assertEqual(called, {'Mixin1.random'})
+
+ class SubClass8(Mixin2, Mixin1, random.Random):
+ pass
+ called = set()
+ SubClass8().randrange(42)
+ self.assertEqual(called, {'Mixin2.getrandbits'})
+
 
 class TestModule(unittest.TestCase):
 def testMagicConstants(self):
