cpython: 91d7fadac271 (original) (raw)

Mercurial > cpython

changeset 90152:91d7fadac271

Issue #21136: Avoid unnecessary normalization in Fractions resulting from power and other operations. [#21136]

Mark Dickinson dickinsm@gmail.com
date	Sat, 05 Apr 2014 09:29:00 +0100
parents	087cdbf49e80
children	9acc8196a82c
files	Lib/fractions.py Lib/test/test_fractions.py Misc/NEWS
diffstat	3 files changed, 19 insertions(+), 10 deletions(-)[+] [-] Lib/fractions.py 23 Lib/test/test_fractions.py 3 Misc/NEWS 3

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line diff

--- a/Lib/fractions.py +++ b/Lib/fractions.py @@ -70,7 +70,7 @@ class Fraction(numbers.Rational): slots = ('_numerator', '_denominator') # We're immutable, so use new not init

def new(cls, numerator=0, denominator=None):

def new(cls, numerator=0, denominator=None, _normalize=True): """Constructs a Rational.

Takes a string like '3/2' or '1.5', another Rational instance, a @@ -165,9 +165,12 @@ class Fraction(numbers.Rational): if denominator == 0: raise ZeroDivisionError('Fraction(%s, 0)' % numerator)

   g = gcd(numerator, denominator)[](#l1.16)

   self._numerator = numerator // g[](#l1.17)

   self._denominator = denominator // g[](#l1.18)

```
   if _normalize:[](#l1.19)
```

       g = gcd(numerator, denominator)[](#l1.20)

```
       numerator //= g[](#l1.21)
```
```
       denominator //= g[](#l1.22)
```

   self._numerator = numerator[](#l1.23)

   self._denominator = denominator[](#l1.24)
   return self[](#l1.25)

@classmethod @@ -453,10 +456,12 @@ class Fraction(numbers.Rational): power = b.numerator if power >= 0: return Fraction(a._numerator ** power,

                               a._denominator ** power)[](#l1.32)

                               a._denominator ** power,[](#l1.33)

                               _normalize=False)[](#l1.34)
           else:[](#l1.35)
               return Fraction(a._denominator ** -power,[](#l1.36)

                               a._numerator ** -power)[](#l1.37)

                               a._numerator ** -power,[](#l1.38)

                               _normalize=False)[](#l1.39)
       else:[](#l1.40)
           # A fractional power will generally produce an[](#l1.41)
           # irrational number.[](#l1.42)

@@ -480,15 +485,15 @@ class Fraction(numbers.Rational): def pos(a): """+a: Coerces a subclass instance to Fraction"""

   return Fraction(a._numerator, a._denominator)[](#l1.47)

   return Fraction(a._numerator, a._denominator, _normalize=False)[](#l1.48)

def neg(a): """-a"""

   return Fraction(-a._numerator, a._denominator)[](#l1.52)

   return Fraction(-a._numerator, a._denominator, _normalize=False)[](#l1.53)

def abs(a): """abs(a)"""

   return Fraction(abs(a._numerator), a._denominator)[](#l1.57)

   return Fraction(abs(a._numerator), a._denominator, _normalize=False)[](#l1.58)

def trunc(a): """trunc(a)"""

--- a/Lib/test/test_fractions.py +++ b/Lib/test/test_fractions.py @@ -330,7 +330,6 @@ class FractionTest(unittest.TestCase): self.assertTypedEquals(F(-2, 10), round(F(-15, 100), 1)) self.assertTypedEquals(F(-2, 10), round(F(-25, 100), 1)) - def testArithmetic(self): self.assertEqual(F(1, 2), F(1, 10) + F(2, 5)) self.assertEqual(F(-3, 10), F(1, 10) - F(2, 5)) @@ -402,6 +401,8 @@ class FractionTest(unittest.TestCase): self.assertTypedEquals(2.0 , 4 ** F(1, 2)) self.assertTypedEquals(0.25, 2.0 ** F(-2, 1)) self.assertTypedEquals(1.0 + 0j, (1.0 + 0j) ** F(1, 10))

   self.assertRaises(ZeroDivisionError, operator.pow,[](#l2.15)

                     F(0, 1), -2)[](#l2.16)

def testMixingWithDecimal(self): # Decimal refuses mixed arithmetic (but not mixed comparisons)

--- a/Misc/NEWS +++ b/Misc/NEWS @@ -29,6 +29,9 @@ Core and Builtins Library ------- +- Issue #21136: Avoid unnecessary normalization of Fractions resulting from

power and other operations. Patch by Raymond Hettinger. +

Issue #17621: Introduce importlib.util.LazyLoader.
Issue #21076: signal module constants were turned into enums.