bpo-40541: Add optional *counts* parameter to random.sample() (GH-19970)
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
index bb95ca0..a3710f4 100644
--- a/Lib/test/test_random.py
+++ b/Lib/test/test_random.py
@@ -9,7 +9,7 @@
from math import log, exp, pi, fsum, sin, factorial
from test import support
from fractions import Fraction
-
+from collections import Counter
class TestBasicOps:
# Superclass with tests common to all generators.
@@ -161,6 +161,77 @@
population = {10, 20, 30, 40, 50, 60, 70}
self.gen.sample(population, k=5)
+ 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_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 = random.sample
+ seed = random.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 test_choices(self):
choices = self.gen.choices
data = ['red', 'green', 'blue', 'yellow']