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bpo-40046: Increase test coverage of the random module #19114

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6e9e44b
bpo-40046: Increase test coverage of the random module
serhiy-storchaka Mar 23, 2020
6ab03bb
Update Doc/library/random.rst
serhiy-storchaka Mar 23, 2020
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4 changes: 2 additions & 2 deletions Doc/library/random.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -119,8 +119,8 @@ Functions for integers
randrange(start, stop[, step])

Return a randomly selected element from ``range(start, stop, step)``. This is
equivalent to ``choice(range(start, stop, step))``, but doesn't actually build a
range object.
equivalent to ``choice(range(start, stop, step))``, but acceps also numbers
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with integer value like ``3.0`` and doesn't actually build a range object.

The positional argument pattern matches that of :func:`range`. Keyword arguments
should not be used because the function may use them in unexpected ways.
Expand Down
35 changes: 32 additions & 3 deletions Lib/test/test_random.py
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Expand Up @@ -97,6 +97,7 @@ def test_shuffle(self):
shuffle(lst)
self.assertTrue(lst != shuffled_lst)
self.assertRaises(TypeError, shuffle, (1, 2, 3))
self.assertRaises(TypeError, shuffle, {1, 2, 3})

def test_shuffle_random_argument(self):
# Test random argument to shuffle.
Expand All @@ -112,6 +113,10 @@ def test_choice(self):
choice([])
self.assertEqual(choice([50]), 50)
self.assertIn(choice([25, 75]), [25, 75])
self.assertIn(choice((25, 75)), (25, 75))
self.assertIn(choice('abc'), ('a', 'b', 'c'))
self.assertRaises(TypeError, choice, {25, 75})
self.assertRaises(TypeError, choice, iter([25, 75]))

def test_sample(self):
# For the entire allowable range of 0 <= k <= N, validate that
Expand All @@ -127,7 +132,9 @@ def test_sample(self):
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, population, -1)
self.assertRaises(ValueError, self.gen.sample, [], -1)
self.assertRaises(TypeError, self.gen.sample, population, 1.0)

def test_sample_distribution(self):
# For the entire allowable range of 0 <= k <= N, validate that
Expand All @@ -149,9 +156,9 @@ def test_sample_inputs(self):
# SF bug #801342 -- population can be any iterable defining __len__()
self.gen.sample(set(range(20)), 2)
self.gen.sample(range(20), 2)
self.gen.sample(range(20), 2)
self.gen.sample(str('abcdefghijklmnopqrst'), 2)
self.gen.sample(tuple('abcdefghijklmnopqrst'), 2)
self.assertRaises(TypeError, self.gen.sample, iter(range(20)), 2)

def test_sample_on_dicts(self):
self.assertRaises(TypeError, self.gen.sample, dict.fromkeys('abcdef'), 2)
Expand Down Expand Up @@ -187,6 +194,8 @@ def test_choices(self):
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
with self.assertRaises(TypeError):
choices(iter(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))
Expand All @@ -200,14 +209,19 @@ def test_choices(self):
[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)
[True, False, True, False], # booleans (include / exclude)
iter([15, 10, 25, 30]),
]:
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=set(range(4)), k=5)
with self.assertRaises(TypeError):
choices(data, cum_weights=iter(range(4)), k=5)
with self.assertRaises(TypeError):
choices(data, cum_weights=[None]*4, k=5) # non-numeric cum_weights
with self.assertRaises(TypeError):
Expand Down Expand Up @@ -361,18 +375,32 @@ def test_randrange_nonunit_step(self):
rint = self.gen.randrange(0, 2, 2)
self.assertEqual(rint, 0)

def test_randrange_non_integers(self):
randrange = self.gen.randrange
self.assertIn(randrange(3.0), range(3))
self.assertIn(randrange(0, 3.0), range(0, 3))
self.assertIn(randrange(0, 42, 1.0), range(0, 42, 1))
self.assertIn(randrange(0, 42, 3.0), range(0, 42, 3))

def test_randrange_errors(self):
raises = partial(self.assertRaises, ValueError, self.gen.randrange)
randrange = self.gen.randrange
raises = partial(self.assertRaises, ValueError, randrange)
# Empty range
raises(3, 3)
raises(-721)
raises(0, 100, -12)
# Non-integer start/stop
raises(3.14159)
raises('3')
self.assertRaises(TypeError, randrange, [3])
raises(0, 2.71828)
raises(0, '3')
self.assertRaises(TypeError, randrange, 0, [3])
# Zero and non-integer step
raises(0, 42, 0)
raises(0, 42, 3.14159)
raises(0, 42, '3')
self.assertRaises(TypeError, randrange, 0, 42, [3])

def test_genrandbits(self):
# Verify ranges
Expand All @@ -392,6 +420,7 @@ def test_genrandbits(self):
self.assertRaises(TypeError, self.gen.getrandbits, 1, 2)
self.assertRaises(ValueError, self.gen.getrandbits, 0)
self.assertRaises(ValueError, self.gen.getrandbits, -1)
self.assertRaises(TypeError, self.gen.getrandbits, 10.0)
self.assertRaises(TypeError, self.gen.getrandbits, 10.1)

def test_randbelow_logic(self, _log=log, int=int):
Expand Down