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Revert change in r60712: turn alternate constructors back into

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classmethods instead of staticmethods.
This commit is contained in:
Mark Dickinson 2008-02-12 21:40:53 +00:00
parent e1b824793a
commit 0aa52a1658
1 changed files with 13 additions and 13 deletions
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26
Lib/fractions.py
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@ -106,39 +106,39 @@ class Fraction(Rational):
self._denominator = int(denominator // g) self._denominator = int(denominator // g)
return self return self
@staticmethod @classmethod
def from_float(f): def from_float(cls, f):
"""Converts a finite float to a rational number, exactly. """Converts a finite float to a rational number, exactly.
Beware that Fraction.from_float(0.3) != Fraction(3, 10). Beware that Fraction.from_float(0.3) != Fraction(3, 10).
""" """
if not isinstance(f, float): if not isinstance(f, float):
raise TypeError("Fraction.from_float() only takes floats, " raise TypeError("%s.from_float() only takes floats, not %r (%s)" %
"not %r (%s)" % (f, type(f).__name__)) (cls.__name__, f, type(f).__name__))
if math.isnan(f) or math.isinf(f): if math.isnan(f) or math.isinf(f):
raise TypeError("Cannot convert %r to Fraction." % f) raise TypeError("Cannot convert %r to %s." % (f, cls.__name__))
return Fraction(*f.as_integer_ratio()) return cls(*f.as_integer_ratio())
@staticmethod @classmethod
def from_decimal(dec): def from_decimal(cls, dec):
"""Converts a finite Decimal instance to a rational number, exactly.""" """Converts a finite Decimal instance to a rational number, exactly."""
from decimal import Decimal from decimal import Decimal
if not isinstance(dec, Decimal): if not isinstance(dec, Decimal):
raise TypeError( raise TypeError(
"Fraction.from_decimal() only takes Decimals, not %r (%s)" % "%s.from_decimal() only takes Decimals, not %r (%s)" %
(dec, type(dec).__name__)) (cls.__name__, dec, type(dec).__name__))
if not dec.is_finite(): if not dec.is_finite():
# Catches infinities and nans. # Catches infinities and nans.
raise TypeError("Cannot convert %s to Fraction." % dec) raise TypeError("Cannot convert %s to %s." % (dec, cls.__name__))
sign, digits, exp = dec.as_tuple() sign, digits, exp = dec.as_tuple()
digits = int(''.join(map(str, digits))) digits = int(''.join(map(str, digits)))
if sign: if sign:
digits = -digits digits = -digits
if exp >= 0: if exp >= 0:
return Fraction(digits * 10 ** exp) return cls(digits * 10 ** exp)
else: else:
return Fraction(digits, 10 ** -exp) return cls(digits, 10 ** -exp)
def limit_denominator(self, max_denominator=1000000): def limit_denominator(self, max_denominator=1000000):
"""Closest Fraction to self with denominator at most max_denominator. """Closest Fraction to self with denominator at most max_denominator.