1 files changed, 20 insertions, 1 deletions
diff --git a/Lib/numbers.py b/Lib/numbers.py
index ed815ef41eb..0634f62ff12 100644
--- a/Lib/numbers.py
+++ b/Lib/numbers.py
@@ -148,7 +148,7 @@ class Real(Complex):
     """To Complex, Real adds the operations that work on real numbers.
 
     In short, those are: a conversion to float, trunc(), divmod,
-    %, <, <=, >, and >=.
+    is_integer, %, <, <=, >, and >=.
 
     Real also provides defaults for the derived operations.
     """
@@ -242,6 +242,17 @@ class Real(Complex):
         """self <= other"""
         raise NotImplementedError
 
+    def is_integer(self):
+        """Return True if the Real is integral; otherwise return False.
+
+        This default implementation can be overridden in subclasses
+        for performance reasons or to deal with values such as NaN,
+        which would otherwise cause an exception to be raised.
+        """
+        # Although __int__ is not defined at this level, the int
+        # constructor falls back to __trunc__, which we do have.
+        return self == int(self)
+
     # Concrete implementations of Complex abstract methods.
     def __complex__(self):
         """complex(self) == complex(float(self), 0)"""
@@ -290,6 +301,10 @@ class Rational(Real):
         """
         return self.numerator / self.denominator
 
+    def is_integer(self):
+        """Return True if the Rational is integral; otherwise return False."""
+        return self.denominator == 1
+
 
 class Integral(Rational):
     """Integral adds a conversion to int and the bit-string operations."""
@@ -386,4 +401,8 @@ class Integral(Rational):
         """Integers have a denominator of 1."""
         return 1
 
+    def is_integer(self):
+        """Return True; all Integrals represent an integral value."""
+        return True
+
 Integral.register(int)