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Code Issues Projects Releases Packages Wiki Activity Actions 8

GH-81620: Add random.binomialvariate() (GH-94719)

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Raymond Hettinger 2022-07-13 09:46:04 -05:00 • committed by GitHub
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4 changed files with 175 additions and 8 deletions
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56
Lib/test/test_random.py
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@ -1045,6 +1045,9 @@ class TestDistributions(unittest.TestCase):
(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),
@ -1052,6 +1055,59 @@ class TestDistributions(unittest.TestCase):
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(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 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].