Fraction literals should support underscores in numbers and whitespace around numbers

[rhettinger]

To make fraction literals more readable, this should be made to work: Fraction('31_415_925_535 / 10_000_000_000')

PEP 515 – Underscores in Numeric Literals are well supported in all numeric types except for fractions. This works: 1_234 and Decimal('1_234'). However, this is not accepted: Fraction('1_234').

Like decimals and ints, fractions support leading and trailing whitespace for string inputs: int(' 123 '), Decimal(' 123.4 '), and Fraction(' 123/100 '). What is still needed is support for optional whitespace around the forward slash: Fraction('355 / 113'). This particular example came up when using the Fraction module to teach math to kids and where the string literal was obtained from calling input().

Side note: If you write print(355/113) in your code, Black will reformat it to print(355 / 113). Because of this, I expect that adults will also develop a preference for writing fractions with whitespace around the slash.

[mdickinson]

See also #88512

[mdickinson]

this should be made to work: Fraction('31_415_925_535 / 10_000_000_000')

Agreed on the underscores, both for readability and for consistency with int.

+1 to allowing whitespace around the slash, too.

I don't agree with the slippery slope argument in #88512 (comment). complex has all sorts of oddities both in parsing and printing, and I don't see any need for those to limit what seem like fairly natural enhancements for Fraction.

[mdickinson]

FTR, underscore support was added previously in #26422