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  r71832 | mark.dickinson | 2009-04-24 14:56:07 +0100 (Fri, 24 Apr 2009) | 3 lines

  Issue #5812: The two-argument form of the Fraction constructor
  now accepts arbitrary Rational instances.
........
This commit is contained in:
Mark Dickinson 2009-04-24 14:06:19 +00:00
parent f21bd3cc2f
commit d4d95f8eac
3 changed files with 32 additions and 13 deletions
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33
Lib/fractions.py
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@ -54,7 +54,7 @@ class Fraction(numbers.Rational):
__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 Rational.
Takes a string like '3/2' or '1.5', another Rational, or a
@ -63,8 +63,13 @@ class Fraction(numbers.Rational):
"""
self = super(Fraction, cls).__new__(cls)
if not isinstance(numerator, int) and denominator == 1:
if isinstance(numerator, str):
if denominator is None:
if isinstance(numerator, numbers.Rational):
self._numerator = numerator.numerator
self._denominator = numerator.denominator
return self
elif isinstance(numerator, str):
# Handle construction from strings.
m = _RATIONAL_FORMAT.match(numerator)
if m is None:
@ -91,18 +96,22 @@ class Fraction(numbers.Rational):
if m.group('sign') == '-':
numerator = -numerator
elif isinstance(numerator, numbers.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, numbers.Rational) and
isinstance(denominator, numbers.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