Add a subtract() method to collections.Counter()
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index 797b350..1bd49d9 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -661,6 +661,16 @@
set_result = setop(set(p.elements()), set(q.elements()))
self.assertEqual(counter_result, dict.fromkeys(set_result, 1))
+ def test_subtract(self):
+ c = Counter(a=-5, b=0, c=5, d=10, e=15,g=40)
+ c.subtract(a=1, b=2, c=-3, d=10, e=20, f=30, h=-50)
+ self.assertEqual(c, Counter(a=-6, b=-2, c=8, d=0, e=-5, f=-30, g=40, h=50))
+ c = Counter(a=-5, b=0, c=5, d=10, e=15,g=40)
+ c.subtract(Counter(a=1, b=2, c=-3, d=10, e=20, f=30, h=-50))
+ self.assertEqual(c, Counter(a=-6, b=-2, c=8, d=0, e=-5, f=-30, g=40, h=50))
+ c = Counter('aaabbcd')
+ c.subtract('aaaabbcce')
+ self.assertEqual(c, Counter(a=-1, b=0, c=-1, d=1, e=-1))
class TestOrderedDict(unittest.TestCase):