#22464: Speed up common Fraction operations by special-casing several

birkenfeld · birkenfeld · commit 40f9735486a8 · 2014-09-24T08:37:55.000+02:00
operations for int-type arguments: constructor and equality test.

Also avoid redundant property lookups in addition and subtraction.
diff --git a/Lib/fractions.py b/Lib/fractions.py
@@ -104,7 +104,12 @@ def __new__(cls, numerator=0, denominator=None, _normalize=True):
         self = super(Fraction, cls).__new__(cls)
 
         if denominator is None:
-            if isinstance(numerator, numbers.Rational):
+            if type(numerator) is int:
+                self._numerator = numerator
+                self._denominator = 1
+                return self
+
+            elif isinstance(numerator, numbers.Rational):
                 self._numerator = numerator.numerator
                 self._denominator = numerator.denominator
                 return self
@@ -153,6 +158,9 @@ def __new__(cls, numerator=0, denominator=None, _normalize=True):
                 raise TypeError("argument should be a string "
                                 "or a Rational instance")
 
+        elif type(numerator) is int is type(denominator):
+            pass  # *very* normal case
+
         elif (isinstance(numerator, numbers.Rational) and
             isinstance(denominator, numbers.Rational)):
             numerator, denominator = (
@@ -399,17 +407,17 @@ def reverse(b, a):
 
     def _add(a, b):
         """a + b"""
-        return Fraction(a.numerator * b.denominator +
-                        b.numerator * a.denominator,
-                        a.denominator * b.denominator)
+        da, db = a.denominator, b.denominator
+        return Fraction(a.numerator * db + b.numerator * da,
+                        da * db)
 
     __add__, __radd__ = _operator_fallbacks(_add, operator.add)
 
     def _sub(a, b):
         """a - b"""
-        return Fraction(a.numerator * b.denominator -
-                        b.numerator * a.denominator,
-                        a.denominator * b.denominator)
+        da, db = a.denominator, b.denominator
+        return Fraction(a.numerator * db - b.numerator * da,
+                        da * db)
 
     __sub__, __rsub__ = _operator_fallbacks(_sub, operator.sub)
 
@@ -561,6 +569,8 @@ def __hash__(self):
 
     def __eq__(a, b):
         """a == b"""
+        if type(b) is int:
+            return a._numerator == b and a._denominator == 1
         if isinstance(b, numbers.Rational):
             return (a._numerator == b.numerator and
                     a._denominator == b.denominator)
