[Python-checkins] r71832 - in python/trunk: Lib/fractions.py Lib/test/test_fractions.py Misc/NEWS
mark.dickinson
python-checkins at python.org
Fri Apr 24 15:56:07 CEST 2009
Author: mark.dickinson
Date: Fri Apr 24 15:56:07 2009
New Revision: 71832
Log:
Issue #5812: The two-argument form of the Fraction constructor
now accepts arbitrary Rational instances.
Modified:
python/trunk/Lib/fractions.py
python/trunk/Lib/test/test_fractions.py
python/trunk/Misc/NEWS
Modified: python/trunk/Lib/fractions.py
==============================================================================
--- python/trunk/Lib/fractions.py (original)
+++ python/trunk/Lib/fractions.py Fri Apr 24 15:56:07 2009
@@ -56,7 +56,7 @@
__slots__ = ('_numerator', '_denominator')
# We're immutable, so use __new__ not __init__
- def __new__(cls, numerator=0, denominator=1):
+ def __new__(cls, numerator=0, denominator=None):
"""Constructs a Fraction.
Takes a string like '3/2' or '1.5', another Fraction, or a
@@ -65,8 +65,13 @@
"""
self = super(Fraction, cls).__new__(cls)
- if type(numerator) not in (int, long) and denominator == 1:
- if isinstance(numerator, basestring):
+ if denominator is None:
+ if isinstance(numerator, Rational):
+ self._numerator = numerator.numerator
+ self._denominator = numerator.denominator
+ return self
+
+ elif isinstance(numerator, basestring):
# Handle construction from strings.
m = _RATIONAL_FORMAT.match(numerator)
if m is None:
@@ -93,18 +98,22 @@
if m.group('sign') == '-':
numerator = -numerator
- 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
+ else:
+ raise TypeError("argument should be a string "
+ "or a Rational instance")
+
+ elif (isinstance(numerator, Rational) and
+ isinstance(denominator, Rational)):
+ numerator, denominator = (
+ numerator.numerator * denominator.denominator,
+ denominator.numerator * numerator.denominator
+ )
+ else:
+ raise TypeError("both arguments should be "
+ "Rational instances")
if denominator == 0:
raise ZeroDivisionError('Fraction(%s, 0)' % numerator)
- numerator = operator.index(numerator)
- denominator = operator.index(denominator)
g = gcd(numerator, denominator)
self._numerator = numerator // g
self._denominator = denominator // g
Modified: python/trunk/Lib/test/test_fractions.py
==============================================================================
--- python/trunk/Lib/test/test_fractions.py (original)
+++ python/trunk/Lib/test/test_fractions.py Fri Apr 24 15:56:07 2009
@@ -60,13 +60,19 @@
self.assertEquals((7, 15), _components(F(7, 15)))
self.assertEquals((10**23, 1), _components(F(10**23)))
+ self.assertEquals((3, 77), _components(F(F(3, 7), 11)))
+ self.assertEquals((-9, 5), _components(F(2, F(-10, 9))))
+ self.assertEquals((2486, 2485), _components(F(F(22, 7), F(355, 113))))
+
self.assertRaisesMessage(ZeroDivisionError, "Fraction(12, 0)",
F, 12, 0)
self.assertRaises(TypeError, F, 1.5)
self.assertRaises(TypeError, F, 1.5 + 3j)
- self.assertRaises(TypeError, F, F(1, 2), 3)
self.assertRaises(TypeError, F, "3/2", 3)
+ self.assertRaises(TypeError, F, 3, 0j)
+ self.assertRaises(TypeError, F, 3, 1j)
+
def testFromString(self):
self.assertEquals((5, 1), _components(F("5")))
Modified: python/trunk/Misc/NEWS
==============================================================================
--- python/trunk/Misc/NEWS (original)
+++ python/trunk/Misc/NEWS Fri Apr 24 15:56:07 2009
@@ -244,6 +244,10 @@
Library
-------
+- Issue #5812: For the two-argument form of the Fraction constructor,
+ Fraction(m, n), m and n are permitted to be arbitrary Rational
+ instances.
+
- Issue #5812: Fraction('1e6') is valid: more generally, any string
that's valid for float() is now valid for Fraction(), with the
exception of strings representing NaNs and infinities.
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