[issue37836] Support .as_integer_ratio() in fractions.Fraction

[Raymond Hettinger]

Raymond Hettinger  added the comment:

I don't think this is a door we should open:

   >>> Fraction(3.5, 2.5)
   Fraction(7, 5)

This currently raises a useful exception:

   TypeError: both arguments should be Rational instances

That is especially helpful in avoiding cases like this:

>>> Fraction(1.1, 3.3)
Fraction(2476979795053773, 7430939385161318)

If that output is desired, the two conversions should be explicit.

>>> Fraction(1.1) / Fraction(3.3)
Fraction(2476979795053773, 7430939385161318

I recommend rejecting this feature request as being more likely to be hazardous 
than helpful.

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[issue37836] Support .as_integer_ratio() in fractions.Fraction

[Jeroen Demeyer]

Jeroen Demeyer  added the comment:

> I afraid this can slow down the Fraction constructor.

No, it doesn't! It even speeds up the constructor in some cases:

./python -m perf timeit --duplicate 200 -s 'from fractions import Fraction; x = 
1' 'Fraction(x)'
BEFORE: Mean +- std dev: 826 ns +- 20 ns
AFTER:  Mean +- std dev: 814 ns +- 17 ns

./python -m perf timeit --duplicate 200 -s 'from fractions import Fraction; x = 
1' 'Fraction(x, x)'
BEFORE: Mean +- std dev: 1.44 us +- 0.03 us
AFTER:  Mean +- std dev: 1.46 us +- 0.02 us

./python -m perf timeit --duplicate 200 -s 'from fractions import Fraction; x = 
Fraction(1)' 'Fraction(x)'
BEFORE: Mean +- std dev: 1.64 us +- 0.03 us
AFTER:  Mean +- std dev: 1.30 us +- 0.04 us

./python -m perf timeit --duplicate 200 -s 'from fractions import Fraction; x = 
Fraction(1)' 'Fraction(x, x)'
BEFORE: Mean +- std dev: 3.03 us +- 0.05 us
AFTER:  Mean +- std dev: 2.34 us +- 0.06 us

./python -m perf timeit --duplicate 200 -s 'from fractions import Fraction; x = 
1.0' 'Fraction(x)'
BEFORE: Mean +- std dev: 1.82 us +- 0.02 us
AFTER:  Mean +- std dev: 1.29 us +- 0.04 us

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[issue37836] Support .as_integer_ratio() in fractions.Fraction

[Jeroen Demeyer]

Jeroen Demeyer  added the comment:

> See issue37884 which uses a C accelerator.

Note that that doesn't replace this issue, because I need to support 
as_integer_ratio both in the *numerator* and *denominator*.

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[issue37836] Support .as_integer_ratio() in fractions.Fraction

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

See issue37884 which uses a C accelerator.

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[issue37836] Support .as_integer_ratio() in fractions.Fraction

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

I afraid this can slow down the Fraction constructor.

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[issue37836] Support .as_integer_ratio() in fractions.Fraction

[Jeroen Demeyer]

Change by Jeroen Demeyer :


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pull_requests: +15046
pull_request: https://github.com/python/cpython/pull/15328

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[issue37836] Support .as_integer_ratio() in fractions.Fraction

[Jeroen Demeyer]

Change by Jeroen Demeyer :


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keywords: +patch
pull_requests: +15045
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/15327

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[issue37836] Support .as_integer_ratio() in fractions.Fraction

[Jeroen Demeyer]

New submission from Jeroen Demeyer :

Currently, the fractions.Fraction constructor accepts an .as_integer_ratio() 
method only for the specific types "float" and "Decimal". It would be good to 
support this for arbitrary classes.

This is part of what was proposed in #37822, but without adding the 
math.operator() function.

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components: Library (Lib)
messages: 349536
nosy: jdemeyer, mark.dickinson, rhettinger, serhiy.storchaka, stutzbach
priority: normal
severity: normal
status: open
title: Support .as_integer_ratio() in fractions.Fraction
versions: Python 3.9

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