Handle iterable inputs. Add some tests

python · rhettinger · May 28, 2020 · May 24, 2020 · May 24, 2020 · May 24, 2020
commit 6a471a1c021ed48163f2e0e8cfd0b943f36099b6
diff --git a/Lib/collections/__init__.py b/Lib/collections/__init__.py
@@ -894,18 +894,26 @@ def isequal(self, other):
         Unlike the __eq__() method, this test ignores counts that
         are zero or negative.
         '''
+        if not isinstance(other, Counter):
+            other = Counter(other)
         return +self == +other
 
     def issubset(self, other):
         'True if positive counts in self <= counts in other.'
+        if not isinstance(other, Counter):
+            other = Counter(other)
         return not self - other
 
     def issuperset(self, other):
         'True if positive counts in self >= counts in other.'
+        if not isinstance(other, Counter):
+            other = Counter(other)
         return not other - self
 
     def isdisjoint(self, other):
         'True is none of the elements in self overlap with other'
+        if not isinstance(other, Counter):
+            other = Counter(other)
         return not self & other
 
     # Rich comparison operators for multiset subset and superset tests
@@ -920,7 +928,7 @@ def __lt__(self, other):
             'Rich comparison operators have been deliberately omitted. '
             'Use the isequal(), issubset(), and issuperset() methods instead.')
     __le__ = __gt__ = __ge__ = __lt__
-    
+
 
 ########################################################################
 ###  ChainMap

diff --git 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 +2220,25 @@ def test_helper_function(self):
         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('abc', 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))
+
 
 ################################################################################
 ### Run tests