Benchmark	ref	patch
Fraction(myint)	5.62 us	7.03 us: 1.25x slower
Fraction(Fraction(1, 2))	5.89 us	4.88 us: 1.21x faster
Fraction(Decimal('0.25'))	11.1 us	7.98 us: 1.39x faster
Fraction(IntSubclass(123))	5.93 us	5.05 us: 1.17x faster
Fraction(FloatSubclass(0.25))	7.69 us	4.26 us: 1.81x faster
Fraction('123')	19.2 us	16.1 us: 1.19x faster
Fraction('1/3')	19.6 us	16.4 us: 1.20x faster
Fraction('1.2e-3')	26.1 us	23.0 us: 1.14x faster
Fraction('-.2')	23.4 us	20.2 us: 1.16x faster
Geometric mean	(ref)	1.21x faster

# bench.pyimportpyperffromfractionsimportFractionasFfromdecimalimportDecimalasDfromnumbersimportIntegralrunner=pyperf.Runner()s='Fraction'classMyInt:numerator=123denominator=1def__int__(self):return123def__repr__(self):return"myint"classIntSubclass(int):def__repr__(self):return'IntSubclass('+super().__repr__()+')'classFloatSubclass(float):def__repr__(self):return'FloatSubclass('+super().__repr__()+')'Integral.register(MyInt)forvin [MyInt(),F(1,2),D("0.25"),IntSubclass(123),FloatSubclass(0.25),"123","1/3","1.2e-3","-.2"]:r=s+'('+repr(v)+')'runner.bench_func(r,F,v)

pythongh-72902: improve Fraction constructor speed for typical inputs

1c67935

This moves abc check for numbers.Rational - down.

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May 20, 2025

Fractions instantiation revisited#72902

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May 20, 2025

skirpichev mentioned this pull request

May 20, 2025

gh-72902: improve Fraction(str) speed (don't use regexp's)#133994

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eendebakpt commentedMay 20, 2025

There is a slight behaviour change here: forFraction subclasses the construction now goes via.as_integer_ratio, instead of via.numerator and.denumerator (for this reason the benchmarkFraction(Fraction(1, 2)) is improving).

A minimal example:

import fractionsclass MyFraction(Fraction):    @property    def numerator(self):        print('he!')        return super().numeratorf = MyFraction(1,2)Fraction(f)

I think the change is acceptable and would probably accept the PR.

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skirpichev commentedMay 20, 2025

>>>help(fractions.Fraction.as_integer_ratio)Help on function as_integer_ratio in module fractions:as_integer_ratio(self)    Return a pair of integers, whose ratio is equal to the original Fraction.    The ratio is in lowest terms and has a positive denominator.