gh-72902: speedup Fraction.from_decimal/float in typical cases #133251
+13
−10
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Here patch2 is the current version. v1 had a hack to check # bench.py
import pyperf
from fractions import Fraction as F
from decimal import Decimal as D
from numbers import Integral
runner = pyperf.Runner()
s = 'Fraction.from_decimal'
f = F.from_decimal
class myint:
numerator = 123
denominator = 1
def __int__(self):
return 123
def __repr__(self):
return "myint"
Integral.register(myint)
for v in [1, myint(), D(1)]:
r = s + '(' + repr(v) + ')'
runner.bench_func(r, f, v)
s = 'Fraction.from_float'
f = F.from_float
for v in [1, myint(), 1.1]:
r = s + '(' + repr(v) + ')'
runner.bench_func(r, f, v)diff --git a/Lib/fractions.py b/Lib/fractions.py
index fa722589fb..d7887af9f8 100644
--- a/Lib/fractions.py
+++ b/Lib/fractions.py
@@ -335,23 +335,23 @@ def from_float(cls, f):
Beware that Fraction.from_float(0.3) != Fraction(3, 10).
"""
- if isinstance(f, numbers.Integral):
+ if not isinstance(f, float):
+ if not isinstance(f, (int, numbers.Integral)):
+ raise TypeError("%s.from_float() only takes floats, not %r (%s)" %
+ (cls.__name__, f, type(f).__name__))
return cls(f)
- elif not isinstance(f, float):
- raise TypeError("%s.from_float() only takes floats, not %r (%s)" %
- (cls.__name__, f, type(f).__name__))
return cls._from_coprime_ints(*f.as_integer_ratio())
@classmethod
def from_decimal(cls, dec):
"""Converts a finite Decimal instance to a rational number, exactly."""
from decimal import Decimal
- if isinstance(dec, numbers.Integral):
- dec = Decimal(int(dec))
- elif not isinstance(dec, Decimal):
- raise TypeError(
- "%s.from_decimal() only takes Decimals, not %r (%s)" %
- (cls.__name__, dec, type(dec).__name__))
+ if not isinstance(dec, Decimal):
+ if not isinstance(dec, (int, numbers.Integral)):
+ raise TypeError(
+ "%s.from_decimal() only takes Decimals, not %r (%s)" %
+ (cls.__name__, dec, type(dec).__name__))
+ dec = int(dec)
return cls._from_coprime_ints(*dec.as_integer_ratio())
@classmethod |
|
This is a second part of improvements, cherry-picked from the issue thread. I think this is less controversial, as speedup affects main use-cases (i.e. Decimal's or float's, respectively). With v2 version we haven't speed regressions for integer case. Though, I'm not sure about using that hack. |
This is slightly slower: |
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