modify dunder methods of +/- inf object for comparison

Author: peterpanmj

pandas/_libs/algos.pyx

@@ -65,22 +65,22 @@ class Infinity(object):
     """ provide a positive Infinity comparision method for ranking """
 
     __lt__ = lambda self, other: False
-    __le__ = lambda self, other: self is other
-    __eq__ = lambda self, other: self is other
-    __ne__ = lambda self, other: self is not other
-    __gt__ = lambda self, other: self is not other
+    __le__ = lambda self, other: isinstance(other, Infinity)
+    __eq__ = lambda self, other: isinstance(other, Infinity)
+    __ne__ = lambda self, other: not isinstance(other, Infinity)
+    __gt__ = lambda self, other: not isinstance(other, Infinity)
     __ge__ = lambda self, other: True
 
 
 class NegInfinity(object):
     """ provide a negative Infinity comparision method for ranking """
 
-    __lt__ = lambda self, other: self is not other
+    __lt__ = lambda self, other: not isinstance(other, NegInfinity)
     __le__ = lambda self, other: True
-    __eq__ = lambda self, other: self is other
-    __ne__ = lambda self, other: self is not other
+    __eq__ = lambda self, other: isinstance(other, NegInfinity)
+    __ne__ = lambda self, other: not isinstance(other, NegInfinity)
     __gt__ = lambda self, other: False
-    __ge__ = lambda self, other: self is other
+    __ge__ = lambda self, other: isinstance(other, NegInfinity)
 
 
 @cython.wraparound(False)