import unittest import unittest.mock import random import os import time import pickle import warnings import test.support from functools import partial from math import log, exp, pi, fsum, sin, factorial from test import support from fractions import Fraction from collections import abc, Counter class TestBasicOps: # Superclass with tests common to all generators. # Subclasses must arrange for self.gen to retrieve the Random instance # to be tested. def randomlist(self, n): """Helper function to make a list of random numbers""" return [self.gen.random() for i in range(n)] def test_autoseed(self): self.gen.seed() state1 = self.gen.getstate() time.sleep(0.1) self.gen.seed() # different seeds at different times state2 = self.gen.getstate() self.assertNotEqual(state1, state2) def test_saverestore(self): N = 1000 self.gen.seed() state = self.gen.getstate() randseq = self.randomlist(N) self.gen.setstate(state) # should regenerate the same sequence self.assertEqual(randseq, self.randomlist(N)) def test_seedargs(self): # Seed value with a negative hash. class MySeed(object): def __hash__(self): return -1729 for arg in [None, 0, 1, -1, 10**20, -(10**20), False, True, 3.14, 'a']: self.gen.seed(arg) for arg in [1+2j, tuple('abc'), MySeed()]: with self.assertRaises(TypeError): self.gen.seed(arg) for arg in [list(range(3)), dict(one=1)]: self.assertRaises(TypeError, self.gen.seed, arg) 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 # randomness source is not found. To test this on machines where it # exists, run the above test, test_seedargs(), again after mocking # os.urandom() so that it raises the exception expected when the # randomness source is not available. urandom_mock.side_effect = NotImplementedError self.test_seedargs() def test_shuffle(self): shuffle = self.gen.shuffle lst = [] shuffle(lst) self.assertEqual(lst, []) lst = [37] shuffle(lst) self.assertEqual(lst, [37]) seqs = [list(range(n)) for n in range(10)] shuffled_seqs = [list(range(n)) for n in range(10)] for shuffled_seq in shuffled_seqs: shuffle(shuffled_seq) for (seq, shuffled_seq) in zip(seqs, shuffled_seqs): self.assertEqual(len(seq), len(shuffled_seq)) self.assertEqual(set(seq), set(shuffled_seq)) # The above tests all would pass if the shuffle was a # no-op. The following non-deterministic test covers that. It # asserts that the shuffled sequence of 1000 distinct elements # must be different from the original one. Although there is # mathematically a non-zero probability that this could # actually happen in a genuinely random shuffle, it is # completely negligible, given that the number of possible # permutations of 1000 objects is 1000! (factorial of 1000), # which is considerably larger than the number of atoms in the # universe... lst = list(range(1000)) shuffled_lst = list(range(1000)) shuffle(shuffled_lst) self.assertTrue(lst != shuffled_lst) shuffle(lst) self.assertTrue(lst != shuffled_lst) self.assertRaises(TypeError, shuffle, (1, 2, 3)) def test_choice(self): choice = self.gen.choice with self.assertRaises(IndexError): choice([]) self.assertEqual(choice([50]), 50) self.assertIn(choice([25, 75]), [25, 75]) def test_choice_with_numpy(self): # Accommodation for NumPy arrays which have disabled __bool__(). # See: https://github.com/python/cpython/issues/100805 choice = self.gen.choice class NA(list): "Simulate numpy.array() behavior" def __bool__(self): raise RuntimeError with self.assertRaises(IndexError): choice(NA([])) self.assertEqual(choice(NA([50])), 50) self.assertIn(choice(NA([25, 75])), [25, 75]) def test_sample(self): # For the entire allowable range of 0 <= k <= N, validate that # the sample is of the correct length and contains only unique items N = 100 population = range(N) for k in range(N+1): s = self.gen.sample(population, k) self.assertEqual(len(s), k) uniq = set(s) self.assertEqual(len(uniq), k) self.assertTrue(uniq <= set(population)) self.assertEqual(self.gen.sample([], 0), []) # test edge case N==k==0 # Exception raised if size of sample exceeds that of population self.assertRaises(ValueError, self.gen.sample, population, N+1) self.assertRaises(ValueError, self.gen.sample, [], -1) def test_sample_distribution(self): # For the entire allowable range of 0 <= k <= N, validate that # sample generates all possible permutations n = 5 pop = range(n) trials = 10000 # large num prevents false negatives without slowing normal case for k in range(n): expected = factorial(n) // factorial(n-k) perms = {} for i in range(trials): perms[tuple(self.gen.sample(pop, k))] = None if len(perms) == expected: break else: self.fail() def test_sample_inputs(self): # SF bug #801342 -- population can be any iterable defining __len__() self.gen.sample(range(20), 2) self.gen.sample(range(20), 2) self.gen.sample(str('abcdefghijklmnopqrst'), 2) self.gen.sample(tuple('abcdefghijklmnopqrst'), 2) def test_sample_on_dicts(self): self.assertRaises(TypeError, self.gen.sample, dict.fromkeys('abcdef'), 2) def test_sample_on_sets(self): with self.assertRaises(TypeError): population = {10, 20, 30, 40, 50, 60, 70} self.gen.sample(population, k=5) def test_sample_on_seqsets(self): class SeqSet(abc.Sequence, abc.Set): def __init__(self, items): self._items = items def __len__(self): return len(self._items) def __getitem__(self, index): return self._items[index] population = SeqSet([2, 4, 1, 3]) with warnings.catch_warnings(): warnings.simplefilter("error", DeprecationWarning) self.gen.sample(population, k=2) def test_sample_with_counts(self): sample = self.gen.sample # General case colors = ['red', 'green', 'blue', 'orange', 'black', 'brown', 'amber'] counts = [500, 200, 20, 10, 5, 0, 1 ] k = 700 summary = Counter(sample(colors, counts=counts, k=k)) self.assertEqual(sum(summary.values()), k) for color, weight in zip(colors, counts): self.assertLessEqual(summary[color], weight) self.assertNotIn('brown', summary) # Case that exhausts the population k = sum(counts) summary = Counter(sample(colors, counts=counts, k=k)) self.assertEqual(sum(summary.values()), k) for color, weight in zip(colors, counts): self.assertLessEqual(summary[color], weight) self.assertNotIn('brown', summary) # Case with population size of 1 summary = Counter(sample(['x'], counts=[10], k=8)) self.assertEqual(summary, Counter(x=8)) # Case with all counts equal. nc = len(colors) summary = Counter(sample(colors, counts=[10]*nc, k=10*nc)) self.assertEqual(summary, Counter(10*colors)) # Test error handling with self.assertRaises(TypeError): sample(['red', 'green', 'blue'], counts=10, k=10) # counts not iterable with self.assertRaises(ValueError): sample(['red', 'green', 'blue'], counts=[-3, -7, -8], k=2) # counts are negative with self.assertRaises(ValueError): sample(['red', 'green', 'blue'], counts=[0, 0, 0], k=2) # counts are zero with self.assertRaises(ValueError): sample(['red', 'green'], counts=[10, 10], k=21) # population too small with self.assertRaises(ValueError): sample(['red', 'green', 'blue'], counts=[1, 2], k=2) # too few counts with self.assertRaises(ValueError): sample(['red', 'green', 'blue'], counts=[1, 2, 3, 4], k=2) # too many counts def test_choices(self): choices = self.gen.choices data = ['red', 'green', 'blue', 'yellow'] str_data = 'abcd' range_data = range(4) set_data = set(range(4)) # basic functionality for sample in [ choices(data, k=5), choices(data, range(4), k=5), choices(k=5, population=data, weights=range(4)), choices(k=5, population=data, cum_weights=range(4)), ]: self.assertEqual(len(sample), 5) self.assertEqual(type(sample), list) self.assertTrue(set(sample) <= set(data)) # test argument handling with self.assertRaises(TypeError): # missing arguments choices(2) self.assertEqual(choices(data, k=0), []) # k == 0 self.assertEqual(choices(data, k=-1), []) # negative k behaves like ``[0] * -1`` with self.assertRaises(TypeError): choices(data, k=2.5) # k is a float self.assertTrue(set(choices(str_data, k=5)) <= set(str_data)) # population is a string sequence self.assertTrue(set(choices(range_data, k=5)) <= set(range_data)) # population is a range with self.assertRaises(TypeError): choices(set_data, k=2) # population is not a sequence self.assertTrue(set(choices(data, None, k=5)) <= set(data)) # weights is None self.assertTrue(set(choices(data, weights=None, k=5)) <= set(data)) with self.assertRaises(ValueError): choices(data, [1,2], k=5) # len(weights) != len(population) with self.assertRaises(TypeError): choices(data, 10, k=5) # non-iterable weights with self.assertRaises(TypeError): choices(data, [None]*4, k=5) # non-numeric weights for weights in [ [15, 10, 25, 30], # integer weights [15.1, 10.2, 25.2, 30.3], # float weights [Fraction(1, 3), Fraction(2, 6), Fraction(3, 6), Fraction(4, 6)], # fractional weights [True, False, True, False] # booleans (include / exclude) ]: self.assertTrue(set(choices(data, weights, k=5)) <= set(data)) with self.assertRaises(ValueError): choices(data, cum_weights=[1,2], k=5) # len(weights) != len(population) with self.assertRaises(TypeError): choices(data, cum_weights=10, k=5) # non-iterable cum_weights with self.assertRaises(TypeError): choices(data, cum_weights=[None]*4, k=5) # non-numeric cum_weights with self.assertRaises(TypeError): choices(data, range(4), cum_weights=range(4), k=5) # both weights and cum_weights for weights in [ [15, 10, 25, 30], # integer cum_weights [15.1, 10.2, 25.2, 30.3], # float cum_weights [Fraction(1, 3), Fraction(2, 6), Fraction(3, 6), Fraction(4, 6)], # fractional cum_weights ]: self.assertTrue(set(choices(data, cum_weights=weights, k=5)) <= set(data)) # Test weight focused on a single element of the population self.assertEqual(choices('abcd', [1, 0, 0, 0]), ['a']) self.assertEqual(choices('abcd', [0, 1, 0, 0]), ['b']) self.assertEqual(choices('abcd', [0, 0, 1, 0]), ['c']) self.assertEqual(choices('abcd', [0, 0, 0, 1]), ['d']) # Test consistency with random.choice() for empty population with self.assertRaises(IndexError): choices([], k=1) with self.assertRaises(IndexError): choices([], weights=[], k=1) with self.assertRaises(IndexError): choices([], cum_weights=[], k=5) def test_choices_subnormal(self): # Subnormal weights would occasionally trigger an IndexError # in choices() when the value returned by random() was large # enough to make `random() * total` round up to the total. # See https://bugs.python.org/msg275594 for more detail. choices = self.gen.choices choices(population=[1, 2], weights=[1e-323, 1e-323], k=5000) def test_choices_with_all_zero_weights(self): # See issue #38881 with self.assertRaises(ValueError): self.gen.choices('AB', [0.0, 0.0]) def test_choices_negative_total(self): with self.assertRaises(ValueError): self.gen.choices('ABC', [3, -5, 1]) def test_choices_infinite_total(self): with self.assertRaises(ValueError): self.gen.choices('A', [float('inf')]) with self.assertRaises(ValueError): self.gen.choices('AB', [0.0, float('inf')]) with self.assertRaises(ValueError): self.gen.choices('AB', [-float('inf'), 123]) with self.assertRaises(ValueError): self.gen.choices('AB', [0.0, float('nan')]) with self.assertRaises(ValueError): self.gen.choices('AB', [float('-inf'), float('inf')]) def test_gauss(self): # Ensure that the seed() method initializes all the hidden state. In # particular, through 2.2.1 it failed to reset a piece of state used # by (and only by) the .gauss() method. for seed in 1, 12, 123, 1234, 12345, 123456, 654321: self.gen.seed(seed) x1 = self.gen.random() y1 = self.gen.gauss(0, 1) self.gen.seed(seed) x2 = self.gen.random() y2 = self.gen.gauss(0, 1) self.assertEqual(x1, x2) self.assertEqual(y1, y2) def test_getrandbits(self): # Verify ranges for k in range(1, 1000): self.assertTrue(0 <= self.gen.getrandbits(k) < 2**k) self.assertEqual(self.gen.getrandbits(0), 0) # Verify all bits active getbits = self.gen.getrandbits for span in [1, 2, 3, 4, 31, 32, 32, 52, 53, 54, 119, 127, 128, 129]: all_bits = 2**span-1 cum = 0 cpl_cum = 0 for i in range(100): v = getbits(span) cum |= v cpl_cum |= all_bits ^ v self.assertEqual(cum, all_bits) self.assertEqual(cpl_cum, all_bits) # Verify argument checking self.assertRaises(TypeError, self.gen.getrandbits) self.assertRaises(TypeError, self.gen.getrandbits, 1, 2) self.assertRaises(ValueError, self.gen.getrandbits, -1) self.assertRaises(TypeError, self.gen.getrandbits, 10.1) def test_pickling(self): for proto in range(pickle.HIGHEST_PROTOCOL + 1): state = pickle.dumps(self.gen, proto) origseq = [self.gen.random() for i in range(10)] newgen = pickle.loads(state) restoredseq = [newgen.random() for i in range(10)] self.assertEqual(origseq, restoredseq) def test_bug_1727780(self): # verify that version-2-pickles can be loaded # fine, whether they are created on 32-bit or 64-bit # platforms, and that version-3-pickles load fine. files = [("randv2_32.pck", 780), ("randv2_64.pck", 866), ("randv3.pck", 343)] for file, value in files: with open(support.findfile(file),"rb") as f: r = pickle.load(f) self.assertEqual(int(r.random()*1000), value) def test_bug_9025(self): # Had problem with an uneven distribution in int(n*random()) # Verify the fix by checking that distributions fall within expectations. n = 100000 randrange = self.gen.randrange k = sum(randrange(6755399441055744) % 3 == 2 for i in range(n)) self.assertTrue(0.30 < k/n < .37, (k/n)) def test_randbytes(self): # Verify ranges for n in range(1, 10): data = self.gen.randbytes(n) self.assertEqual(type(data), bytes) self.assertEqual(len(data), n) self.assertEqual(self.gen.randbytes(0), b'') # Verify argument checking self.assertRaises(TypeError, self.gen.randbytes) self.assertRaises(TypeError, self.gen.randbytes, 1, 2) self.assertRaises(ValueError, self.gen.randbytes, -1) self.assertRaises(TypeError, self.gen.randbytes, 1.0) def test_mu_sigma_default_args(self): self.assertIsInstance(self.gen.normalvariate(), float) self.assertIsInstance(self.gen.gauss(), float) try: random.SystemRandom().random() except NotImplementedError: SystemRandom_available = False else: SystemRandom_available = True @unittest.skipUnless(SystemRandom_available, "random.SystemRandom not available") class SystemRandom_TestBasicOps(TestBasicOps, unittest.TestCase): gen = random.SystemRandom() def test_autoseed(self): # Doesn't need to do anything except not fail self.gen.seed() def test_saverestore(self): self.assertRaises(NotImplementedError, self.gen.getstate) self.assertRaises(NotImplementedError, self.gen.setstate, None) def test_seedargs(self): # Doesn't need to do anything except not fail self.gen.seed(100) def test_gauss(self): self.gen.gauss_next = None self.gen.seed(100) self.assertEqual(self.gen.gauss_next, None) def test_pickling(self): for proto in range(pickle.HIGHEST_PROTOCOL + 1): self.assertRaises(NotImplementedError, pickle.dumps, self.gen, proto) def test_53_bits_per_float(self): # This should pass whenever a C double has 53 bit precision. span = 2 ** 53 cum = 0 for i in range(100): cum |= int(self.gen.random() * span) self.assertEqual(cum, span-1) def test_bigrand(self): # The randrange routine should build-up the required number of bits # in stages so that all bit positions are active. span = 2 ** 500 cum = 0 for i in range(100): r = self.gen.randrange(span) self.assertTrue(0 <= r < span) cum |= r self.assertEqual(cum, span-1) def test_bigrand_ranges(self): for i in [40,80, 160, 200, 211, 250, 375, 512, 550]: start = self.gen.randrange(2 ** (i-2)) stop = self.gen.randrange(2 ** i) if stop <= start: continue self.assertTrue(start <= self.gen.randrange(start, stop) < stop) def test_rangelimits(self): for start, stop in [(-2,0), (-(2**60)-2,-(2**60)), (2**60,2**60+2)]: self.assertEqual(set(range(start,stop)), set([self.gen.randrange(start,stop) for i in range(100)])) def test_randrange_nonunit_step(self): rint = self.gen.randrange(0, 10, 2) self.assertIn(rint, (0, 2, 4, 6, 8)) rint = self.gen.randrange(0, 2, 2) self.assertEqual(rint, 0) def test_randrange_errors(self): raises_value_error = partial(self.assertRaises, ValueError, self.gen.randrange) raises_type_error = partial(self.assertRaises, TypeError, self.gen.randrange) # Empty range raises_value_error(3, 3) raises_value_error(-721) raises_value_error(0, 100, -12) # Zero step raises_value_error(0, 42, 0) raises_type_error(0, 42, 0.0) raises_type_error(0, 0, 0.0) # Non-integer stop raises_type_error(3.14159) raises_type_error(3.0) raises_type_error(Fraction(3, 1)) raises_type_error('3') raises_type_error(0, 2.71827) raises_type_error(0, 2.0) raises_type_error(0, Fraction(2, 1)) raises_type_error(0, '2') raises_type_error(0, 2.71827, 2) # Non-integer start raises_type_error(2.71827, 5) raises_type_error(2.0, 5) raises_type_error(Fraction(2, 1), 5) raises_type_error('2', 5) raises_type_error(2.71827, 5, 2) # Non-integer step raises_type_error(0, 42, 3.14159) raises_type_error(0, 42, 3.0) raises_type_error(0, 42, Fraction(3, 1)) raises_type_error(0, 42, '3') raises_type_error(0, 42, 1.0) raises_type_error(0, 0, 1.0) def test_randrange_step(self): # bpo-42772: When stop is None, the step argument was being ignored. randrange = self.gen.randrange with self.assertRaises(TypeError): randrange(1000, step=100) with self.assertRaises(TypeError): randrange(1000, None, step=100) def test_randbelow_logic(self, _log=log, int=int): # check bitcount transition points: 2**i and 2**(i+1)-1 # show that: k = int(1.001 + _log(n, 2)) # is equal to or one greater than the number of bits in n for i in range(1, 1000): n = 1 << i # check an exact power of two numbits = i+1 k = int(1.00001 + _log(n, 2)) self.assertEqual(k, numbits) self.assertEqual(n, 2**(k-1)) n += n - 1 # check 1 below the next power of two k = int(1.00001 + _log(n, 2)) self.assertIn(k, [numbits, numbits+1]) self.assertTrue(2**k > n > 2**(k-2)) n -= n >> 15 # check a little farther below the next power of two k = int(1.00001 + _log(n, 2)) self.assertEqual(k, numbits) # note the stronger assertion self.assertTrue(2**k > n > 2**(k-1)) # note the stronger assertion class TestRawMersenneTwister(unittest.TestCase): @test.support.cpython_only def test_bug_41052(self): # _random.Random should not be allowed to serialization import _random for proto in range(pickle.HIGHEST_PROTOCOL + 1): r = _random.Random() self.assertRaises(TypeError, pickle.dumps, r, proto) @test.support.cpython_only def test_bug_42008(self): # _random.Random should call seed with first element of arg tuple import _random r1 = _random.Random() r1.seed(8675309) r2 = _random.Random(8675309) self.assertEqual(r1.random(), r2.random()) class MersenneTwister_TestBasicOps(TestBasicOps, unittest.TestCase): gen = random.Random() def test_guaranteed_stable(self): # These sequences are guaranteed to stay the same across versions of python self.gen.seed(3456147, version=1) self.assertEqual([self.gen.random().hex() for i in range(4)], ['0x1.ac362300d90d2p-1', '0x1.9d16f74365005p-1', '0x1.1ebb4352e4c4dp-1', '0x1.1a7422abf9c11p-1']) self.gen.seed("the quick brown fox", version=2) self.assertEqual([self.gen.random().hex() for i in range(4)], ['0x1.1239ddfb11b7cp-3', '0x1.b3cbb5c51b120p-4', '0x1.8c4f55116b60fp-1', '0x1.63eb525174a27p-1']) def test_bug_27706(self): # Verify that version 1 seeds are unaffected by hash randomization self.gen.seed('nofar', version=1) # hash('nofar') == 5990528763808513177 self.assertEqual([self.gen.random().hex() for i in range(4)], ['0x1.8645314505ad7p-1', '0x1.afb1f82e40a40p-5', '0x1.2a59d2285e971p-1', '0x1.56977142a7880p-6']) self.gen.seed('rachel', version=1) # hash('rachel') == -9091735575445484789 self.assertEqual([self.gen.random().hex() for i in range(4)], ['0x1.0b294cc856fcdp-1', '0x1.2ad22d79e77b8p-3', '0x1.3052b9c072678p-2', '0x1.578f332106574p-3']) self.gen.seed('', version=1) # hash('') == 0 self.assertEqual([self.gen.random().hex() for i in range(4)], ['0x1.b0580f98a7dbep-1', '0x1.84129978f9c1ap-1', '0x1.aeaa51052e978p-2', '0x1.092178fb945a6p-2']) def test_bug_31478(self): # There shouldn't be an assertion failure in _random.Random.seed() in # case the argument has a bad __abs__() method. class BadInt(int): def __abs__(self): return None try: self.gen.seed(BadInt()) except TypeError: pass def test_bug_31482(self): # Verify that version 1 seeds are unaffected by hash randomization # when the seeds are expressed as bytes rather than strings. # The hash(b) values listed are the Python2.7 hash() values # which were used for seeding. self.gen.seed(b'nofar', version=1) # hash('nofar') == 5990528763808513177 self.assertEqual([self.gen.random().hex() for i in range(4)], ['0x1.8645314505ad7p-1', '0x1.afb1f82e40a40p-5', '0x1.2a59d2285e971p-1', '0x1.56977142a7880p-6']) self.gen.seed(b'rachel', version=1) # hash('rachel') == -9091735575445484789 self.assertEqual([self.gen.random().hex() for i in range(4)], ['0x1.0b294cc856fcdp-1', '0x1.2ad22d79e77b8p-3', '0x1.3052b9c072678p-2', '0x1.578f332106574p-3']) self.gen.seed(b'', version=1) # hash('') == 0 self.assertEqual([self.gen.random().hex() for i in range(4)], ['0x1.b0580f98a7dbep-1', '0x1.84129978f9c1ap-1', '0x1.aeaa51052e978p-2', '0x1.092178fb945a6p-2']) b = b'\x00\x20\x40\x60\x80\xA0\xC0\xE0\xF0' self.gen.seed(b, version=1) # hash(b) == 5015594239749365497 self.assertEqual([self.gen.random().hex() for i in range(4)], ['0x1.52c2fde444d23p-1', '0x1.875174f0daea4p-2', '0x1.9e9b2c50e5cd2p-1', '0x1.fa57768bd321cp-2']) def test_setstate_first_arg(self): self.assertRaises(ValueError, self.gen.setstate, (1, None, None)) def test_setstate_middle_arg(self): start_state = self.gen.getstate() # Wrong type, s/b tuple self.assertRaises(TypeError, self.gen.setstate, (2, None, None)) # Wrong length, s/b 625 self.assertRaises(ValueError, self.gen.setstate, (2, (1,2,3), None)) # Wrong type, s/b tuple of 625 ints self.assertRaises(TypeError, self.gen.setstate, (2, ('a',)*625, None)) # Last element s/b an int also self.assertRaises(TypeError, self.gen.setstate, (2, (0,)*624+('a',), None)) # Last element s/b between 0 and 624 with self.assertRaises((ValueError, OverflowError)): self.gen.setstate((2, (1,)*624+(625,), None)) with self.assertRaises((ValueError, OverflowError)): self.gen.setstate((2, (1,)*624+(-1,), None)) # Failed calls to setstate() should not have changed the state. bits100 = self.gen.getrandbits(100) self.gen.setstate(start_state) self.assertEqual(self.gen.getrandbits(100), bits100) # Little trick to make "tuple(x % (2**32) for x in internalstate)" # raise ValueError. I cannot think of a simple way to achieve this, so # I am opting for using a generator as the middle argument of setstate # which attempts to cast a NaN to integer. state_values = self.gen.getstate()[1] state_values = list(state_values) state_values[-1] = float('nan') state = (int(x) for x in state_values) self.assertRaises(TypeError, self.gen.setstate, (2, state, None)) def test_referenceImplementation(self): # Compare the python implementation with results from the original # code. Create 2000 53-bit precision random floats. Compare only # the last ten entries to show that the independent implementations # are tracking. Here is the main() function needed to create the # list of expected random numbers: # void main(void){ # int i; # unsigned long init[4]={61731, 24903, 614, 42143}, length=4; # init_by_array(init, length); # for (i=0; i<2000; i++) { # printf("%.15f ", genrand_res53()); # if (i%5==4) printf("\n"); # } # } expected = [0.45839803073713259, 0.86057815201978782, 0.92848331726782152, 0.35932681119782461, 0.081823493762449573, 0.14332226470169329, 0.084297823823520024, 0.53814864671831453, 0.089215024911993401, 0.78486196105372907] self.gen.seed(61731 + (24903<<32) + (614<<64) + (42143<<96)) actual = self.randomlist(2000)[-10:] for a, e in zip(actual, expected): self.assertAlmostEqual(a,e,places=14) def test_strong_reference_implementation(self): # Like test_referenceImplementation, but checks for exact bit-level # equality. This should pass on any box where C double contains # at least 53 bits of precision (the underlying algorithm suffers # no rounding errors -- all results are exact). from math import ldexp expected = [0x0eab3258d2231f, 0x1b89db315277a5, 0x1db622a5518016, 0x0b7f9af0d575bf, 0x029e4c4db82240, 0x04961892f5d673, 0x02b291598e4589, 0x11388382c15694, 0x02dad977c9e1fe, 0x191d96d4d334c6] self.gen.seed(61731 + (24903<<32) + (614<<64) + (42143<<96)) actual = self.randomlist(2000)[-10:] for a, e in zip(actual, expected): self.assertEqual(int(ldexp(a, 53)), e) def test_long_seed(self): # This is most interesting to run in debug mode, just to make sure # nothing blows up. Under the covers, a dynamically resized array # is allocated, consuming space proportional to the number of bits # in the seed. Unfortunately, that's a quadratic-time algorithm, # so don't make this horribly big. seed = (1 << (10000 * 8)) - 1 # about 10K bytes self.gen.seed(seed) def test_53_bits_per_float(self): # This should pass whenever a C double has 53 bit precision. span = 2 ** 53 cum = 0 for i in range(100): cum |= int(self.gen.random() * span) self.assertEqual(cum, span-1) def test_bigrand(self): # The randrange routine should build-up the required number of bits # in stages so that all bit positions are active. span = 2 ** 500 cum = 0 for i in range(100): r = self.gen.randrange(span) self.assertTrue(0 <= r < span) cum |= r self.assertEqual(cum, span-1) def test_bigrand_ranges(self): for i in [40,80, 160, 200, 211, 250, 375, 512, 550]: start = self.gen.randrange(2 ** (i-2)) stop = self.gen.randrange(2 ** i) if stop <= start: continue self.assertTrue(start <= self.gen.randrange(start, stop) < stop) def test_rangelimits(self): for start, stop in [(-2,0), (-(2**60)-2,-(2**60)), (2**60,2**60+2)]: self.assertEqual(set(range(start,stop)), set([self.gen.randrange(start,stop) for i in range(100)])) def test_getrandbits(self): super().test_getrandbits() # Verify cross-platform repeatability self.gen.seed(1234567) self.assertEqual(self.gen.getrandbits(100), 97904845777343510404718956115) def test_randrange_uses_getrandbits(self): # Verify use of getrandbits by randrange # Use same seed as in the cross-platform repeatability test # in test_getrandbits above. self.gen.seed(1234567) # If randrange uses getrandbits, it should pick getrandbits(100) # when called with a 100-bits stop argument. self.assertEqual(self.gen.randrange(2**99), 97904845777343510404718956115) def test_randbelow_logic(self, _log=log, int=int): # check bitcount transition points: 2**i and 2**(i+1)-1 # show that: k = int(1.001 + _log(n, 2)) # is equal to or one greater than the number of bits in n for i in range(1, 1000): n = 1 << i # check an exact power of two numbits = i+1 k = int(1.00001 + _log(n, 2)) self.assertEqual(k, numbits) self.assertEqual(n, 2**(k-1)) n += n - 1 # check 1 below the next power of two k = int(1.00001 + _log(n, 2)) self.assertIn(k, [numbits, numbits+1]) self.assertTrue(2**k > n > 2**(k-2)) n -= n >> 15 # check a little farther below the next power of two k = int(1.00001 + _log(n, 2)) self.assertEqual(k, numbits) # note the stronger assertion self.assertTrue(2**k > n > 2**(k-1)) # note the stronger assertion def test_randbelow_without_getrandbits(self): # Random._randbelow() can only use random() when the built-in one # has been overridden but no new getrandbits() method was supplied. maxsize = 1<= maxsize) self.gen._randbelow_without_getrandbits( maxsize+1, maxsize=maxsize ) self.gen._randbelow_without_getrandbits(5640, maxsize=maxsize) # This might be going too far to test a single line, but because of our # noble aim of achieving 100% test coverage we need to write a case in # which the following line in Random._randbelow() gets executed: # # rem = maxsize % n # limit = (maxsize - rem) / maxsize # r = random() # while r >= limit: # r = random() # <== *This line* <==< # # Therefore, to guarantee that the while loop is executed at least # once, we need to mock random() so that it returns a number greater # than 'limit' the first time it gets called. n = 42 epsilon = 0.01 limit = (maxsize - (maxsize % n)) / maxsize with unittest.mock.patch.object(random.Random, 'random') as random_mock: random_mock.side_effect = [limit + epsilon, limit - epsilon] self.gen._randbelow_without_getrandbits(n, maxsize=maxsize) self.assertEqual(random_mock.call_count, 2) def test_randrange_bug_1590891(self): start = 1000000000000 stop = -100000000000000000000 step = -200 x = self.gen.randrange(start, stop, step) self.assertTrue(stop < x <= start) self.assertEqual((x+stop)%step, 0) def test_choices_algorithms(self): # The various ways of specifying weights should produce the same results choices = self.gen.choices n = 104729 self.gen.seed(8675309) a = self.gen.choices(range(n), k=10000) self.gen.seed(8675309) b = self.gen.choices(range(n), [1]*n, k=10000) self.assertEqual(a, b) self.gen.seed(8675309) c = self.gen.choices(range(n), cum_weights=range(1, n+1), k=10000) self.assertEqual(a, c) # American Roulette population = ['Red', 'Black', 'Green'] weights = [18, 18, 2] cum_weights = [18, 36, 38] expanded_population = ['Red'] * 18 + ['Black'] * 18 + ['Green'] * 2 self.gen.seed(9035768) a = self.gen.choices(expanded_population, k=10000) self.gen.seed(9035768) b = self.gen.choices(population, weights, k=10000) self.assertEqual(a, b) self.gen.seed(9035768) c = self.gen.choices(population, cum_weights=cum_weights, k=10000) self.assertEqual(a, c) def test_randbytes(self): super().test_randbytes() # Mersenne Twister randbytes() is deterministic # and does not depend on the endian and bitness. seed = 8675309 expected = b'3\xa8\xf9f\xf4\xa4\xd06\x19\x8f\x9f\x82\x02oe\xf0' self.gen.seed(seed) self.assertEqual(self.gen.randbytes(16), expected) # randbytes(0) must not consume any entropy self.gen.seed(seed) self.assertEqual(self.gen.randbytes(0), b'') self.assertEqual(self.gen.randbytes(16), expected) # Four randbytes(4) calls give the same output than randbytes(16) self.gen.seed(seed) self.assertEqual(b''.join([self.gen.randbytes(4) for _ in range(4)]), expected) # Each randbytes(1), randbytes(2) or randbytes(3) call consumes # 4 bytes of entropy self.gen.seed(seed) expected1 = expected[3::4] self.assertEqual(b''.join(self.gen.randbytes(1) for _ in range(4)), expected1) self.gen.seed(seed) expected2 = b''.join(expected[i + 2: i + 4] for i in range(0, len(expected), 4)) self.assertEqual(b''.join(self.gen.randbytes(2) for _ in range(4)), expected2) self.gen.seed(seed) expected3 = b''.join(expected[i + 1: i + 4] for i in range(0, len(expected), 4)) self.assertEqual(b''.join(self.gen.randbytes(3) for _ in range(4)), expected3) def test_randbytes_getrandbits(self): # There is a simple relation between randbytes() and getrandbits() seed = 2849427419 gen2 = random.Random() self.gen.seed(seed) gen2.seed(seed) for n in range(9): self.assertEqual(self.gen.randbytes(n), gen2.getrandbits(n * 8).to_bytes(n, 'little')) def test_sample_counts_equivalence(self): # Test the documented strong equivalence to a sample with repeated elements. # We run this test on random.Random() which makes deterministic selections # for a given seed value. sample = self.gen.sample seed = self.gen.seed colors = ['red', 'green', 'blue', 'orange', 'black', 'amber'] counts = [500, 200, 20, 10, 5, 1 ] k = 700 seed(8675309) s1 = sample(colors, counts=counts, k=k) seed(8675309) expanded = [color for (color, count) in zip(colors, counts) for i in range(count)] self.assertEqual(len(expanded), sum(counts)) s2 = sample(expanded, k=k) self.assertEqual(s1, s2) pop = 'abcdefghi' counts = [10, 9, 8, 7, 6, 5, 4, 3, 2] seed(8675309) s1 = ''.join(sample(pop, counts=counts, k=30)) expanded = ''.join([letter for (letter, count) in zip(pop, counts) for i in range(count)]) seed(8675309) s2 = ''.join(sample(expanded, k=30)) self.assertEqual(s1, s2) def gamma(z, sqrt2pi=(2.0*pi)**0.5): # Reflection to right half of complex plane if z < 0.5: return pi / sin(pi*z) / gamma(1.0-z) # Lanczos approximation with g=7 az = z + (7.0 - 0.5) return az ** (z-0.5) / exp(az) * sqrt2pi * fsum([ 0.9999999999995183, 676.5203681218835 / z, -1259.139216722289 / (z+1.0), 771.3234287757674 / (z+2.0), -176.6150291498386 / (z+3.0), 12.50734324009056 / (z+4.0), -0.1385710331296526 / (z+5.0), 0.9934937113930748e-05 / (z+6.0), 0.1659470187408462e-06 / (z+7.0), ]) class TestDistributions(unittest.TestCase): def test_zeroinputs(self): # Verify that distributions can handle a series of zero inputs' g = random.Random() x = [g.random() for i in range(50)] + [0.0]*5 g.random = x[:].pop; g.uniform(1,10) g.random = x[:].pop; g.paretovariate(1.0) g.random = x[:].pop; g.expovariate(1.0) g.random = x[:].pop; g.expovariate() g.random = x[:].pop; g.weibullvariate(1.0, 1.0) g.random = x[:].pop; g.vonmisesvariate(1.0, 1.0) g.random = x[:].pop; g.normalvariate(0.0, 1.0) g.random = x[:].pop; g.gauss(0.0, 1.0) g.random = x[:].pop; g.lognormvariate(0.0, 1.0) g.random = x[:].pop; g.vonmisesvariate(0.0, 1.0) g.random = x[:].pop; g.gammavariate(0.01, 1.0) g.random = x[:].pop; g.gammavariate(1.0, 1.0) g.random = x[:].pop; g.gammavariate(200.0, 1.0) g.random = x[:].pop; g.betavariate(3.0, 3.0) g.random = x[:].pop; g.triangular(0.0, 1.0, 1.0/3.0) def test_avg_std(self): # Use integration to test distribution average and standard deviation. # Only works for distributions which do not consume variates in pairs g = random.Random() N = 5000 x = [i/float(N) for i in range(1,N)] for variate, args, mu, sigmasqrd in [ (g.uniform, (1.0,10.0), (10.0+1.0)/2, (10.0-1.0)**2/12), (g.triangular, (0.0, 1.0, 1.0/3.0), 4.0/9.0, 7.0/9.0/18.0), (g.expovariate, (1.5,), 1/1.5, 1/1.5**2), (g.vonmisesvariate, (1.23, 0), pi, pi**2/3), (g.paretovariate, (5.0,), 5.0/(5.0-1), 5.0/((5.0-1)**2*(5.0-2))), (g.weibullvariate, (1.0, 3.0), gamma(1+1/3.0), gamma(1+2/3.0)-gamma(1+1/3.0)**2) ]: g.random = x[:].pop y = [] for i in range(len(x)): try: y.append(variate(*args)) except IndexError: pass s1 = s2 = 0 for e in y: s1 += e s2 += (e - mu) ** 2 N = len(y) self.assertAlmostEqual(s1/N, mu, places=2, msg='%s%r' % (variate.__name__, args)) self.assertAlmostEqual(s2/(N-1), sigmasqrd, places=2, msg='%s%r' % (variate.__name__, args)) def test_constant(self): g = random.Random() N = 100 for variate, args, expected in [ (g.uniform, (10.0, 10.0), 10.0), (g.triangular, (10.0, 10.0), 10.0), (g.triangular, (10.0, 10.0, 10.0), 10.0), (g.expovariate, (float('inf'),), 0.0), (g.vonmisesvariate, (3.0, float('inf')), 3.0), (g.gauss, (10.0, 0.0), 10.0), (g.lognormvariate, (0.0, 0.0), 1.0), (g.lognormvariate, (-float('inf'), 0.0), 0.0), (g.normalvariate, (10.0, 0.0), 10.0), (g.binomialvariate, (0, 0.5), 0), (g.binomialvariate, (10, 0.0), 0), (g.binomialvariate, (10, 1.0), 10), (g.paretovariate, (float('inf'),), 1.0), (g.weibullvariate, (10.0, float('inf')), 10.0), (g.weibullvariate, (0.0, 10.0), 0.0), ]: for i in range(N): self.assertEqual(variate(*args), expected) def test_binomialvariate(self): B = random.binomialvariate # Cover all the code paths with self.assertRaises(ValueError): B(n=-1) # Negative n with self.assertRaises(ValueError): B(n=1, p=-0.5) # Negative p with self.assertRaises(ValueError): B(n=1, p=1.5) # p > 1.0 self.assertEqual(B(0, 0.5), 0) # n == 0 self.assertEqual(B(10, 0.0), 0) # p == 0.0 self.assertEqual(B(10, 1.0), 10) # p == 1.0 self.assertTrue(B(1, 0.3) in {0, 1}) # n == 1 fast path self.assertTrue(B(1, 0.9) in {0, 1}) # n == 1 fast path self.assertTrue(B(1, 0.0) in {0}) # n == 1 fast path self.assertTrue(B(1, 1.0) in {1}) # n == 1 fast path # BG method very small p self.assertEqual(B(5, 1e-18), 0) # BG method p <= 0.5 and n*p=1.25 self.assertTrue(B(5, 0.25) in set(range(6))) # BG method p >= 0.5 and n*(1-p)=1.25 self.assertTrue(B(5, 0.75) in set(range(6))) # BTRS method p <= 0.5 and n*p=25 self.assertTrue(B(100, 0.25) in set(range(101))) # BTRS method p > 0.5 and n*(1-p)=25 self.assertTrue(B(100, 0.75) in set(range(101))) # Statistical tests chosen such that they are # exceedingly unlikely to ever fail for correct code. # BG code path # Expected dist: [31641, 42188, 21094, 4688, 391] c = Counter(B(4, 0.25) for i in range(100_000)) self.assertTrue(29_641 <= c[0] <= 33_641, c) self.assertTrue(40_188 <= c[1] <= 44_188) self.assertTrue(19_094 <= c[2] <= 23_094) self.assertTrue(2_688 <= c[3] <= 6_688) self.assertEqual(set(c), {0, 1, 2, 3, 4}) # BTRS code path # Sum of c[20], c[21], c[22], c[23], c[24] expected to be 36,214 c = Counter(B(100, 0.25) for i in range(100_000)) self.assertTrue(34_214 <= c[20]+c[21]+c[22]+c[23]+c[24] <= 38_214) self.assertTrue(set(c) <= set(range(101))) self.assertEqual(c.total(), 100_000) # Demonstrate the BTRS works for huge values of n self.assertTrue(19_000_000 <= B(100_000_000, 0.2) <= 21_000_000) self.assertTrue(89_000_000 <= B(100_000_000, 0.9) <= 91_000_000) def test_von_mises_range(self): # Issue 17149: von mises variates were not consistently in the # range [0, 2*PI]. g = random.Random() N = 100 for mu in 0.0, 0.1, 3.1, 6.2: for kappa in 0.0, 2.3, 500.0: for _ in range(N): sample = g.vonmisesvariate(mu, kappa) self.assertTrue( 0 <= sample <= random.TWOPI, msg=("vonmisesvariate({}, {}) produced a result {} out" " of range [0, 2*pi]").format(mu, kappa, sample)) def test_von_mises_large_kappa(self): # Issue #17141: vonmisesvariate() was hang for large kappas random.vonmisesvariate(0, 1e15) random.vonmisesvariate(0, 1e100) def test_gammavariate_errors(self): # Both alpha and beta must be > 0.0 self.assertRaises(ValueError, random.gammavariate, -1, 3) self.assertRaises(ValueError, random.gammavariate, 0, 2) self.assertRaises(ValueError, random.gammavariate, 2, 0) self.assertRaises(ValueError, random.gammavariate, 1, -3) # There are three different possibilities in the current implementation # of random.gammavariate(), depending on the value of 'alpha'. What we # are going to do here is to fix the values returned by random() to # generate test cases that provide 100% line coverage of the method. @unittest.mock.patch('random.Random.random') def test_gammavariate_alpha_greater_one(self, random_mock): # #1: alpha > 1.0. # We want the first random number to be outside the # [1e-7, .9999999] range, so that the continue statement executes # once. The values of u1 and u2 will be 0.5 and 0.3, respectively. random_mock.side_effect = [1e-8, 0.5, 0.3] returned_value = random.gammavariate(1.1, 2.3) self.assertAlmostEqual(returned_value, 2.53) @unittest.mock.patch('random.Random.random') def test_gammavariate_alpha_equal_one(self, random_mock): # #2.a: alpha == 1. # The execution body of the while loop executes once. # Then random.random() returns 0.45, # which causes while to stop looping and the algorithm to terminate. random_mock.side_effect = [0.45] returned_value = random.gammavariate(1.0, 3.14) self.assertAlmostEqual(returned_value, 1.877208182372648) @unittest.mock.patch('random.Random.random') def test_gammavariate_alpha_equal_one_equals_expovariate(self, random_mock): # #2.b: alpha == 1. # It must be equivalent of calling expovariate(1.0 / beta). beta = 3.14 random_mock.side_effect = [1e-8, 1e-8] gammavariate_returned_value = random.gammavariate(1.0, beta) expovariate_returned_value = random.expovariate(1.0 / beta) self.assertAlmostEqual(gammavariate_returned_value, expovariate_returned_value) @unittest.mock.patch('random.Random.random') def test_gammavariate_alpha_between_zero_and_one(self, random_mock): # #3: 0 < alpha < 1. # This is the most complex region of code to cover, # as there are multiple if-else statements. Let's take a look at the # source code, and determine the values that we need accordingly: # # while 1: # u = random() # b = (_e + alpha)/_e # p = b*u # if p <= 1.0: # <=== (A) # x = p ** (1.0/alpha) # else: # <=== (B) # x = -_log((b-p)/alpha) # u1 = random() # if p > 1.0: # <=== (C) # if u1 <= x ** (alpha - 1.0): # <=== (D) # break # elif u1 <= _exp(-x): # <=== (E) # break # return x * beta # # First, we want (A) to be True. For that we need that: # b*random() <= 1.0 # r1 = random() <= 1.0 / b # # We now get to the second if-else branch, and here, since p <= 1.0, # (C) is False and we take the elif branch, (E). For it to be True, # so that the break is executed, we need that: # r2 = random() <= _exp(-x) # r2 <= _exp(-(p ** (1.0/alpha))) # r2 <= _exp(-((b*r1) ** (1.0/alpha))) _e = random._e _exp = random._exp _log = random._log alpha = 0.35 beta = 1.45 b = (_e + alpha)/_e epsilon = 0.01 r1 = 0.8859296441566 # 1.0 / b r2 = 0.3678794411714 # _exp(-((b*r1) ** (1.0/alpha))) # These four "random" values result in the following trace: # (A) True, (E) False --> [next iteration of while] # (A) True, (E) True --> [while loop breaks] random_mock.side_effect = [r1, r2 + epsilon, r1, r2] returned_value = random.gammavariate(alpha, beta) self.assertAlmostEqual(returned_value, 1.4499999999997544) # Let's now make (A) be False. If this is the case, when we get to the # second if-else 'p' is greater than 1, so (C) evaluates to True. We # now encounter a second if statement, (D), which in order to execute # must satisfy the following condition: # r2 <= x ** (alpha - 1.0) # r2 <= (-_log((b-p)/alpha)) ** (alpha - 1.0) # r2 <= (-_log((b-(b*r1))/alpha)) ** (alpha - 1.0) r1 = 0.8959296441566 # (1.0 / b) + epsilon -- so that (A) is False r2 = 0.9445400408898141 # And these four values result in the following trace: # (B) and (C) True, (D) False --> [next iteration of while] # (B) and (C) True, (D) True [while loop breaks] random_mock.side_effect = [r1, r2 + epsilon, r1, r2] returned_value = random.gammavariate(alpha, beta) self.assertAlmostEqual(returned_value, 1.5830349561760781) @unittest.mock.patch('random.Random.gammavariate') def test_betavariate_return_zero(self, gammavariate_mock): # betavariate() returns zero when the Gamma distribution # that it uses internally returns this same value. 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 class Subclass(random.Random): def __init__(self, newarg=None): random.Random.__init__(self) Subclass(newarg=1) def test_subclasses_overriding_methods(self): # Subclasses with an overridden random, but only the original # getrandbits method should not rely on getrandbits in for randrange, # but should use a getrandbits-independent implementation instead. # subclass providing its own random **and** getrandbits methods # like random.SystemRandom does => keep relying on getrandbits for # randrange class SubClass1(random.Random): def random(self): called.add('SubClass1.random') return random.Random.random(self) def getrandbits(self, n): 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): 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): 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): self.assertAlmostEqual(random.NV_MAGICCONST, 1.71552776992141) self.assertAlmostEqual(random.TWOPI, 6.28318530718) self.assertAlmostEqual(random.LOG4, 1.38629436111989) self.assertAlmostEqual(random.SG_MAGICCONST, 2.50407739677627) def test__all__(self): # tests validity but not completeness of the __all__ list self.assertTrue(set(random.__all__) <= set(dir(random))) @test.support.requires_fork() def test_after_fork(self): # Test the global Random instance gets reseeded in child r, w = os.pipe() pid = os.fork() if pid == 0: # child process try: val = random.getrandbits(128) with open(w, "w") as f: f.write(str(val)) finally: os._exit(0) else: # parent process os.close(w) val = random.getrandbits(128) with open(r, "r") as f: child_val = eval(f.read()) self.assertNotEqual(val, child_val) support.wait_process(pid, exitcode=0) if __name__ == "__main__": unittest.main()