bpo-40755: Add rich comparisons to Counter (GH-20548)

1 files changed, 36 insertions, 86 deletions

diff --git a/Lib/collections/__init__.py b/Lib/collections/__init__.py
index 55fb46c..2acf672 100644
--- a/Lib/collections/__init__.py
+++ b/Lib/collections/__init__.py
@@ -691,6 +691,42 @@ class Counter(dict):
         if elem in self:
             super().__delitem__(elem)
 
+    def __eq__(self, other):
+        'True if all counts agree. Missing counts are treated as zero.'
+        if not isinstance(other, Counter):
+            return NotImplemented
+        return all(self[e] == other[e] for c in (self, other) for e in c)
+
+    def __ne__(self, other):
+        'True if any counts disagree. Missing counts are treated as zero.'
+        if not isinstance(other, Counter):
+            return NotImplemented
+        return not self == other
+
+    def __le__(self, other):
+        'True if all counts in self are a subset of those in other.'
+        if not isinstance(other, Counter):
+            return NotImplemented
+        return all(self[e] <= other[e] for c in (self, other) for e in c)
+
+    def __lt__(self, other):
+        'True if all counts in self are a proper subset of those in other.'
+        if not isinstance(other, Counter):
+            return NotImplemented
+        return self <= other and self != other
+
+    def __ge__(self, other):
+        'True if all counts in self are a superset of those in other.'
+        if not isinstance(other, Counter):
+            return NotImplemented
+        return all(self[e] >= other[e] for c in (self, other) for e in c)
+
+    def __gt__(self, other):
+        'True if all counts in self are a proper superset of those in other.'
+        if not isinstance(other, Counter):
+            return NotImplemented
+        return self >= other and self != other
+
     def __repr__(self):
         if not self:
             return '%s()' % self.__class__.__name__
@@ -886,92 +922,6 @@ class Counter(dict):
                 self[elem] = other_count
         return self._keep_positive()
 
-    def isequal(self, other):
-        ''' Test whether counts agree exactly.
-
-        Negative or missing counts are treated as zero.
-
-        This is different than the inherited __eq__() method which
-        treats negative or missing counts as distinct from zero:
-
-            >>> Counter(a=1, b=0).isequal(Counter(a=1))
-            True
-            >>> Counter(a=1, b=0) == Counter(a=1)
-            False
-
-        Logically equivalent to:  +self == +other
-        '''
-        if not isinstance(other, Counter):
-            other = Counter(other)
-        for elem in set(self) | set(other):
-            left = self[elem]
-            right = other[elem]
-            if left == right:
-                continue
-            if left < 0:
-                left = 0
-            if right < 0:
-                right = 0
-            if left != right:
-                return False
-        return True
-
-    def issubset(self, other):
-        '''True if the counts in self are less than or equal to those in other.
-
-        Negative or missing counts are treated as zero.
-
-        Logically equivalent to:  not self - (+other)
-        '''
-        if not isinstance(other, Counter):
-            other = Counter(other)
-        for elem, count in self.items():
-            other_count = other[elem]
-            if other_count < 0:
-                other_count = 0
-            if count > other_count:
-                return False
-        return True
-
-    def issuperset(self, other):
-        '''True if the counts in self are greater than or equal to those in other.
-
-        Negative or missing counts are treated as zero.
-
-        Logically equivalent to:  not other - (+self)
-        '''
-        if not isinstance(other, Counter):
-            other = Counter(other)
-        return other.issubset(self)
-
-    def isdisjoint(self, other):
-        '''True if none of the elements in self overlap with those in other.
-
-        Negative or missing counts are ignored.
-
-        Logically equivalent to:  not (+self) & (+other)
-        '''
-        if not isinstance(other, Counter):
-            other = Counter(other)
-        for elem, count in self.items():
-            if count > 0 and other[elem] > 0:
-                return False
-        return True
-
-    # Rich comparison operators for multiset subset and superset tests
-    # have been deliberately omitted due to semantic conflicts with the
-    # existing inherited dict equality method.  Subset and superset
-    # semantics ignore zero counts and require that p⊆q ∧ p⊇q ⇔ p=q;
-    # however, that would not be the case for p=Counter(a=1, b=0)
-    # and q=Counter(a=1) where the dictionaries are not equal.
-
-    def _omitted(self, other):
-        raise TypeError(
-            'Rich comparison operators have been deliberately omitted. '
-            'Use the isequal(), issubset(), and issuperset() methods instead.')
-
-    __lt__ = __le__ = __gt__ = __ge__ = __lt__ = _omitted
-
 
 ########################################################################
 ###  ChainMap