Issue37836
Created on 2019-08-13 09:41 by jdemeyer, last changed 2022-04-11 14:59 by admin.
| Pull Requests | |||
|---|---|---|---|
| URL | Status | Linked | Edit |
| PR 15327 | open | jdemeyer, 2019-08-18 21:08 | |
| PR 15328 | open | jdemeyer, 2019-08-18 21:41 | |
| Messages (6) | |||
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| msg349536 - (view) | Author: Jeroen Demeyer (jdemeyer) *  |
Date: 2019-08-13 09:41 | |
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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| msg349933 - (view) | Author: Serhiy Storchaka (serhiy.storchaka) *  |
Date: 2019-08-19 05:02 | |
I afraid this can slow down the Fraction constructor. |
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| msg349940 - (view) | Author: Serhiy Storchaka (serhiy.storchaka) * |
Date: 2019-08-19 06:20 | |
See issue37884 which uses a C accelerator. |
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| msg349942 - (view) | Author: Jeroen Demeyer (jdemeyer) * |
Date: 2019-08-19 08:36 | |
> 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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| msg349945 - (view) | Author: Jeroen Demeyer (jdemeyer) * |
Date: 2019-08-19 09:08 | |
> 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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| msg409531 - (view) | Author: Raymond Hettinger (rhettinger) * |
Date: 2022-01-02 22:00 | |
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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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:59:19 | admin | set | github: 82017 |
| 2022-01-02 22:00:12 | rhettinger | set | messages: + msg409531 |
| 2019-08-19 09:08:06 | jdemeyer | set | messages: + msg349945 |
| 2019-08-19 08:36:44 | jdemeyer | set | messages: + msg349942 |
| 2019-08-19 06:20:20 | serhiy.storchaka | set | messages: + msg349940 |
| 2019-08-19 05:02:46 | serhiy.storchaka | set | messages: + msg349933 |
| 2019-08-18 21:41:06 | jdemeyer | set | pull_requests: + pull_request15046 |
| 2019-08-18 21:08:46 | jdemeyer | set | keywords:
+ patch stage: patch review pull_requests: + pull_request15045 |
| 2019-08-13 09:41:19 | jdemeyer | create | |