[Python-Dev] Symmetry arguments for API expansion (original) (raw)

Tim Peters tim.peters at gmail.com
Tue Mar 13 01:01:50 EDT 2018

[Tim. on as_integer_ratio()]

- I expect the audience is tiny.

[Alexander Belopolsky]

The datetime module would benefit from having asintegerratio() supported by more types. It's been hard to resist requests to allow Decimal in timedelta constructors and/or arithmetics

I don't see the connection. That timedelta construction may use as_integer_ratio() today doesn't mean it has to use as_integer_ratio() forever, and is no reason (to my mind) to add as_integer_ratio all over the place.

Why not drop that, and in oddball cases see whether fractions.Fraction() can handle the input?

fractions.Fraction(decimal.Decimal("1.76")) Fraction(44, 25)

Probably less efficient, but I don't care ;-) And then, e.g., timedelta would also automagically allow Fraction arguments (which, BTW, don't support as_integer_ratio() either). Bonus: if datetime is bothering with hand-coding rational arithmetic now out of concern to get every bit right, Fraction could handle that too by itself.

At heart, the Fraction() constructor is all about creating integer ratios, so is the most natural place to put knowledge of how to do so. A protocol for allowing new numeric types to get converted to Fraction would be more generally useful than just a weird method only datetime uses ;-)

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