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Issue #25971: Optimized creating Fractions from floats by 2 times and from

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Decimals by 3 times.
Unified error messages in float.as_integer_ratio(), Decimal.as_integer_ratio(),
and Fraction constructors.
This commit is contained in:
Serhiy Storchaka 2015-12-29 22:34:23 +02:00
parent 5aab44b301
commit 0d250bc119
5 changed files with 22 additions and 45 deletions
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32
Lib/fractions.py
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@ -125,17 +125,9 @@ class Fraction(numbers.Rational):
self._denominator = numerator.denominator
return self
elif isinstance(numerator, float):
# Exact conversion from float
value = Fraction.from_float(numerator)
self._numerator = value._numerator
self._denominator = value._denominator
return self
elif isinstance(numerator, Decimal):
value = Fraction.from_decimal(numerator)
self._numerator = value._numerator
self._denominator = value._denominator
elif isinstance(numerator, (float, Decimal)):
# Exact conversion
self._numerator, self._denominator = numerator.as_integer_ratio()
return self
elif isinstance(numerator, str):
@ -210,10 +202,6 @@ class Fraction(numbers.Rational):
elif not isinstance(f, float):
raise TypeError("%s.from_float() only takes floats, not %r (%s)" %
(cls.__name__, f, type(f).__name__))
if math.isnan(f):
raise ValueError("Cannot convert %r to %s." % (f, cls.__name__))
if math.isinf(f):
raise OverflowError("Cannot convert %r to %s." % (f, cls.__name__))
return cls(*f.as_integer_ratio())
@classmethod
@ -226,19 +214,7 @@ class Fraction(numbers.Rational):
raise TypeError(
"%s.from_decimal() only takes Decimals, not %r (%s)" %
(cls.__name__, dec, type(dec).__name__))
if dec.is_infinite():
raise OverflowError(
"Cannot convert %s to %s." % (dec, cls.__name__))
if dec.is_nan():
raise ValueError("Cannot convert %s to %s." % (dec, cls.__name__))
sign, digits, exp = dec.as_tuple()
digits = int(''.join(map(str, digits)))
if sign:
digits = -digits
if exp >= 0:
return cls(digits * 10 ** exp)
else:
return cls(digits, 10 ** -exp)
return cls(*dec.as_integer_ratio())
def limit_denominator(self, max_denominator=1000000):
"""Closest Fraction to self with denominator at most max_denominator.