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Performance optimizations on Fraction's constructor. 

./python.exe -m timeit -s 'from fractions import Fraction' 'Fraction(3)`
31.7 usec/loop -> 9.2 usec/loop

  ./python.exe -m timeit -s 'from fractions import Fraction' 'Fraction(3, 2)'`
27.7 usec/loop -> 9.32 usec/loop

  ./python.exe -m timeit -s 'from fractions import Fraction; f = Fraction(3, 2)' 'Fraction(f)'
31.9 usec/loop -> 14.3 usec/loop
This commit is contained in:
Jeffrey Yasskin 2008-02-14 06:12:24 +00:00
parent abe3237187
commit 1c214d6c94
2 changed files with 13 additions and 15 deletions
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20
Lib/fractions.py
View File

@ -64,7 +64,7 @@ class Fraction(Rational):
"""
self = super(Fraction, cls).__new__(cls)
if denominator == 1:
if type(numerator) not in (int, long) and denominator == 1:
if isinstance(numerator, basestring):
# Handle construction from strings.
input = numerator
@ -86,24 +86,22 @@ class Fraction(Rational):
if m.group('sign') == '-':
numerator = -numerator
elif (not isinstance(numerator, numbers.Integral) and
isinstance(numerator, Rational)):
# Handle copies from other rationals.
elif isinstance(numerator, Rational):
# Handle copies from other rationals. Integrals get
# caught here too, but it doesn't matter because
# denominator is already 1.
other_rational = numerator
numerator = other_rational.numerator
denominator = other_rational.denominator
if (not isinstance(numerator, numbers.Integral) or
not isinstance(denominator, numbers.Integral)):
raise TypeError("Fraction(%(numerator)s, %(denominator)s):"
" Both arguments must be integral." % locals())
if denominator == 0:
raise ZeroDivisionError('Fraction(%s, 0)' % numerator)
numerator = numerator.__index__()
denominator = denominator.__index__()
g = gcd(numerator, denominator)
self._numerator = int(numerator // g)
self._denominator = int(denominator // g)
self._numerator = numerator // g
self._denominator = denominator // g
return self
@classmethod

8
Lib/test/test_fractions.py
View File

@ -62,11 +62,11 @@ class FractionTest(unittest.TestCase):
self.assertRaisesMessage(ZeroDivisionError, "Fraction(12, 0)",
F, 12, 0)
self.assertRaises(TypeError, F, 1.5)
self.assertRaises(TypeError, F, 1.5 + 3j)
self.assertRaises(AttributeError, F, 1.5)
self.assertRaises(AttributeError, F, 1.5 + 3j)
self.assertRaises(TypeError, F, F(1, 2), 3)
self.assertRaises(TypeError, F, "3/2", 3)
self.assertRaises(AttributeError, F, F(1, 2), 3)
self.assertRaises(AttributeError, F, "3/2", 3)
def testFromString(self):
self.assertEquals((5, 1), _components(F("5")))