bpo-40755: Add missing multiset operations to Counter() (GH-20339)
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index a8d3337..8d80e88 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -7,6 +7,7 @@
import operator
import pickle
from random import choice, randrange
+from itertools import product, chain, combinations
import string
import sys
from test import support
@@ -2219,6 +2220,64 @@
self.assertTrue(c.called)
self.assertEqual(dict(c), {'a': 5, 'b': 2, 'c': 1, 'd': 1, 'r':2 })
+ def test_multiset_operations_equivalent_to_set_operations(self):
+ # When the multiplicities are all zero or one, multiset operations
+ # are guaranteed to be equivalent to the corresponding operations
+ # for regular sets.
+ s = list(product(('a', 'b', 'c'), range(2)))
+ powerset = chain.from_iterable(combinations(s, r) for r in range(len(s)+1))
+ counters = [Counter(dict(groups)) for groups in powerset]
+ for cp, cq in product(counters, repeat=2):
+ sp = set(cp.elements())
+ sq = set(cq.elements())
+ self.assertEqual(set(cp + cq), sp | sq)
+ self.assertEqual(set(cp - cq), sp - sq)
+ self.assertEqual(set(cp | cq), sp | sq)
+ self.assertEqual(set(cp & cq), sp & sq)
+ self.assertEqual(cp.isequal(cq), sp == sq)
+ self.assertEqual(cp.issubset(cq), sp.issubset(sq))
+ self.assertEqual(cp.issuperset(cq), sp.issuperset(sq))
+ self.assertEqual(cp.isdisjoint(cq), sp.isdisjoint(sq))
+
+ def test_multiset_equal(self):
+ self.assertTrue(Counter(a=3, b=2, c=0).isequal('ababa'))
+ self.assertFalse(Counter(a=3, b=2).isequal('babab'))
+
+ def test_multiset_subset(self):
+ self.assertTrue(Counter(a=3, b=2, c=0).issubset('ababa'))
+ self.assertFalse(Counter(a=3, b=2).issubset('babab'))
+
+ def test_multiset_superset(self):
+ self.assertTrue(Counter(a=3, b=2, c=0).issuperset('aab'))
+ self.assertFalse(Counter(a=3, b=2, c=0).issuperset('aabd'))
+
+ def test_multiset_disjoint(self):
+ self.assertTrue(Counter(a=3, b=2, c=0).isdisjoint('cde'))
+ self.assertFalse(Counter(a=3, b=2, c=0).isdisjoint('bcd'))
+
+ def test_multiset_predicates_with_negative_counts(self):
+ # Multiset predicates run on the output of the elements() method,
+ # meaning that zero counts and negative counts are ignored.
+ # The tests below confirm that we get that same results as the
+ # tests above, even after a negative count has been included
+ # in either *self* or *other*.
+ self.assertTrue(Counter(a=3, b=2, c=0, d=-1).isequal('ababa'))
+ self.assertFalse(Counter(a=3, b=2, d=-1).isequal('babab'))
+ self.assertTrue(Counter(a=3, b=2, c=0, d=-1).issubset('ababa'))
+ self.assertFalse(Counter(a=3, b=2, d=-1).issubset('babab'))
+ self.assertTrue(Counter(a=3, b=2, c=0, d=-1).issuperset('aab'))
+ self.assertFalse(Counter(a=3, b=2, c=0, d=-1).issuperset('aabd'))
+ self.assertTrue(Counter(a=3, b=2, c=0, d=-1).isdisjoint('cde'))
+ self.assertFalse(Counter(a=3, b=2, c=0, d=-1).isdisjoint('bcd'))
+ self.assertTrue(Counter(a=3, b=2, c=0, d=-1).isequal(Counter(a=3, b=2, c=-1)))
+ self.assertFalse(Counter(a=3, b=2, d=-1).isequal(Counter(a=2, b=3, c=-1)))
+ self.assertTrue(Counter(a=3, b=2, c=0, d=-1).issubset(Counter(a=3, b=2, c=-1)))
+ self.assertFalse(Counter(a=3, b=2, d=-1).issubset(Counter(a=2, b=3, c=-1)))
+ self.assertTrue(Counter(a=3, b=2, c=0, d=-1).issuperset(Counter(a=2, b=1, c=-1)))
+ self.assertFalse(Counter(a=3, b=2, c=0, d=-1).issuperset(Counter(a=2, b=1, c=-1, d=1)))
+ self.assertTrue(Counter(a=3, b=2, c=0, d=-1).isdisjoint(Counter(c=1, d=2, e=3, f=-1)))
+ self.assertFalse(Counter(a=3, b=2, c=0, d=-1).isdisjoint(Counter(b=1, c=1, d=1, e=-1)))
+
################################################################################
### Run tests