It is an alternative constructor which only accepts a single numeric argument.
Unlike to Fraction.from_float() and Fraction.from_decimal() it accepts any
real numbers supported by the standard constructor (int, float, Decimal,
Rational numbers, objects with as_integer_ratio()).
Unlike to the standard constructor, it does not accept strings.
Corrected some grammar and spelling issues in documentation.
Co-authored-by: Russell Keith-Magee <russell@keith-magee.com>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
PR #100161 added fancy float-style formatting for the Fraction type,
but left us in a state where basic formatting for fractions (alignment,
fill, minimum width, thousands separators) still wasn't supported.
This PR adds that support.
---------
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Make docstrings for `as_integer_ratio` consistent across types, and document that
the returned pair is always normalized (coprime integers, with positive denominator).
---------
Co-authored-by: Owain Davies <116417456+OTheDev@users.noreply.github.com>
Co-authored-by: Mark Dickinson <dickinsm@gmail.com>
This PR adds support for float-style formatting for `Fraction` objects: it supports the `"e"`, `"E"`, `"f"`, `"F"`, `"g"`, `"G"` and `"%"` presentation types, and all the various bells and whistles of the formatting mini-language for those presentation types. The behaviour almost exactly matches that of `float`, but the implementation works with the exact `Fraction` value and does not do an intermediate conversion to `float`, and so avoids loss of precision or issues with numbers that are outside the dynamic range of the `float` type.
Note that the `"n"` presentation type is _not_ supported. That support could be added later if people have a need for it.
There's one corner-case where the behaviour differs from that of float: for the `float` type, if explicit alignment is specified with a fill character of `'0'` and alignment type `'='`, then thousands separators (if specified) are inserted into the padding string:
```python
>>> format(3.14, '0=11,.2f')
'0,000,003.14'
```
The exact same effect can be achieved by using the `'0'` flag:
```python
>>> format(3.14, '011,.2f')
'0,000,003.14'
```
For `Fraction`, only the `'0'` flag has the above behaviour with respect to thousands separators: there's no special-casing of the particular `'0='` fill-character/alignment combination. Instead, we treat the fill character `'0'` just like any other:
```python
>>> format(Fraction('3.14'), '0=11,.2f')
'00000003.14'
>>> format(Fraction('3.14'), '011,.2f')
'0,000,003.14'
```
The `Fraction` formatter is also stricter about combining these two things: it's not permitted to use both the `'0'` flag _and_ explicit alignment, on the basis that we should refuse the temptation to guess in the face of ambiguity. `float` is less picky:
```python
>>> format(3.14, '0<011,.2f')
'3.140000000'
>>> format(Fraction('3.14'), '0<011,.2f')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Users/mdickinson/Repositories/python/cpython/Lib/fractions.py", line 414, in __format__
raise ValueError(
ValueError: Invalid format specifier '0<011,.2f' for object of type 'Fraction'; can't use explicit alignment when zero-padding
```
* bpo-44258: support PEP 515 for Fraction's initialization from string
* regexps's version
* A different regexps version, which doesn't suffer from catastrophic backtracking
* revert denom -> den
* strip "_" from the decimal str, add few tests
* drop redundant tests
* Add versionchanged & whatsnew entry
* Amend Fraction constructor docs
* Change .. versionchanged:...
Fix regression in fractions.Fraction if the numerator and/or the
denominator is an int subclass. The math.gcd() function is now
used to normalize the numerator and denominator. math.gcd() always
return a int type. Previously, the GCD type depended on numerator
and denominator.
svn+ssh://pythondev@svn.python.org/python/trunk
........
r62490 | benjamin.peterson | 2008-04-24 20:29:10 -0500 (Thu, 24 Apr 2008) | 2 lines
reformat some documentation of classes so methods and attributes are under the class directive
........
svn+ssh://pythondev@svn.python.org/python/trunk
................
r61724 | martin.v.loewis | 2008-03-22 01:01:12 +0100 (Sat, 22 Mar 2008) | 49 lines
Merged revisions 61602-61723 via svnmerge from
svn+ssh://pythondev@svn.python.org/sandbox/trunk/2to3/lib2to3
........
r61626 | david.wolever | 2008-03-19 17:19:16 +0100 (Mi, 19 M?\195?\164r 2008) | 1 line
Added fixer for implicit local imports. See #2414.
........
r61628 | david.wolever | 2008-03-19 17:57:43 +0100 (Mi, 19 M?\195?\164r 2008) | 1 line
Added a class for tests which should not run if a particular import is found.
........
r61629 | collin.winter | 2008-03-19 17:58:19 +0100 (Mi, 19 M?\195?\164r 2008) | 1 line
Two more relative import fixes in pgen2.
........
r61635 | david.wolever | 2008-03-19 20:16:03 +0100 (Mi, 19 M?\195?\164r 2008) | 1 line
Fixed print fixer so it will do the Right Thing when it encounters __future__.print_function. 2to3 gets upset, though, so the tests have been commented out.
........
r61637 | david.wolever | 2008-03-19 21:37:17 +0100 (Mi, 19 M?\195?\164r 2008) | 3 lines
Added a fixer for itertools imports (from itertools import imap, ifilterfalse --> from itertools import filterfalse)
........
r61645 | david.wolever | 2008-03-19 23:22:35 +0100 (Mi, 19 M?\195?\164r 2008) | 1 line
SVN is happier when you add the files you create... -_-'
........
r61654 | david.wolever | 2008-03-20 01:09:56 +0100 (Do, 20 M?\195?\164r 2008) | 1 line
Added an explicit sort order to fixers -- fixes problems like #2427
........
r61664 | david.wolever | 2008-03-20 04:32:40 +0100 (Do, 20 M?\195?\164r 2008) | 3 lines
Fixes#2428 -- comments are no longer eatten by __future__ fixer.
........
r61673 | david.wolever | 2008-03-20 17:22:40 +0100 (Do, 20 M?\195?\164r 2008) | 1 line
Added 2to3 node pretty-printer
........
r61679 | david.wolever | 2008-03-20 20:50:42 +0100 (Do, 20 M?\195?\164r 2008) | 1 line
Made node printing a little bit prettier
........
r61723 | martin.v.loewis | 2008-03-22 00:59:27 +0100 (Sa, 22 M?\195?\164r 2008) | 2 lines
Fix whitespace.
........
................
r61725 | martin.v.loewis | 2008-03-22 01:02:41 +0100 (Sat, 22 Mar 2008) | 2 lines
Install lib2to3.
................
r61731 | facundo.batista | 2008-03-22 03:45:37 +0100 (Sat, 22 Mar 2008) | 4 lines
Small fix that complicated the test actually when that
test failed.
................
r61732 | alexandre.vassalotti | 2008-03-22 05:08:44 +0100 (Sat, 22 Mar 2008) | 2 lines
Added warning for the removal of 'hotshot' in Py3k.
................
r61733 | georg.brandl | 2008-03-22 11:07:29 +0100 (Sat, 22 Mar 2008) | 4 lines
#1918: document that weak references *to* an object are
cleared before the object's __del__ is called, to ensure that the weak
reference callback (if any) finds the object healthy.
................
r61734 | georg.brandl | 2008-03-22 11:56:23 +0100 (Sat, 22 Mar 2008) | 2 lines
Activate the Sphinx doctest extension and convert howto/functional to use it.
................
r61735 | georg.brandl | 2008-03-22 11:58:38 +0100 (Sat, 22 Mar 2008) | 2 lines
Allow giving source names on the cmdline.
................
r61737 | georg.brandl | 2008-03-22 12:00:48 +0100 (Sat, 22 Mar 2008) | 2 lines
Fixup this HOWTO's doctest blocks so that they can be run with sphinx' doctest builder.
................
r61739 | georg.brandl | 2008-03-22 12:47:10 +0100 (Sat, 22 Mar 2008) | 2 lines
Test decimal.rst doctests as far as possible with sphinx doctest.
................
r61741 | georg.brandl | 2008-03-22 13:04:26 +0100 (Sat, 22 Mar 2008) | 2 lines
Make doctests in re docs usable with sphinx' doctest.
................
r61743 | georg.brandl | 2008-03-22 13:59:37 +0100 (Sat, 22 Mar 2008) | 2 lines
Make more doctests in pprint docs testable.
................
r61744 | georg.brandl | 2008-03-22 14:07:06 +0100 (Sat, 22 Mar 2008) | 2 lines
No need to specify explicit "doctest_block" anymore.
................
r61753 | georg.brandl | 2008-03-22 21:08:43 +0100 (Sat, 22 Mar 2008) | 2 lines
Fix-up syntax problems.
................
r61761 | georg.brandl | 2008-03-22 22:06:20 +0100 (Sat, 22 Mar 2008) | 4 lines
Make collections' doctests executable.
(The <BLANKLINE>s will be stripped from presentation output.)
................
r61765 | georg.brandl | 2008-03-22 22:21:57 +0100 (Sat, 22 Mar 2008) | 2 lines
Test doctests in datetime docs.
................
r61766 | georg.brandl | 2008-03-22 22:26:44 +0100 (Sat, 22 Mar 2008) | 2 lines
Test doctests in operator docs.
................
r61767 | georg.brandl | 2008-03-22 22:38:33 +0100 (Sat, 22 Mar 2008) | 2 lines
Enable doctests in functions.rst. Already found two errors :)
................
r61769 | georg.brandl | 2008-03-22 23:04:10 +0100 (Sat, 22 Mar 2008) | 3 lines
Enable doctest running for several other documents.
We have now over 640 doctests that are run with "make doctest".
................
r61773 | raymond.hettinger | 2008-03-23 01:55:46 +0100 (Sun, 23 Mar 2008) | 1 line
Simplify demo code.
................
r61776 | neal.norwitz | 2008-03-23 04:43:33 +0100 (Sun, 23 Mar 2008) | 7 lines
Try to make this test a little more robust and not fail with:
timeout (10.0025) is more than 2 seconds more than expected (0.001)
I'm assuming this problem is caused by DNS lookup. This change
does a DNS lookup of the hostname before trying to connect, so the time
is not included.
................
r61777 | neal.norwitz | 2008-03-23 05:08:30 +0100 (Sun, 23 Mar 2008) | 1 line
Speed up the test by avoiding socket timeouts.
................
r61778 | neal.norwitz | 2008-03-23 05:43:09 +0100 (Sun, 23 Mar 2008) | 1 line
Skip the epoll test if epoll() does not work
................
r61780 | neal.norwitz | 2008-03-23 06:47:20 +0100 (Sun, 23 Mar 2008) | 1 line
Suppress failure (to avoid a flaky test) if we cannot connect to svn.python.org
................
r61781 | neal.norwitz | 2008-03-23 07:13:25 +0100 (Sun, 23 Mar 2008) | 4 lines
Move itertools before future_builtins since the latter depends on the former.
From a clean build importing future_builtins would fail since itertools
wasn't built yet.
................
r61782 | neal.norwitz | 2008-03-23 07:16:04 +0100 (Sun, 23 Mar 2008) | 1 line
Try to prevent the alarm going off early in tearDown
................
r61783 | neal.norwitz | 2008-03-23 07:19:57 +0100 (Sun, 23 Mar 2008) | 4 lines
Remove compiler warnings (on Alpha at least) about using chars as
array subscripts. Using chars are dangerous b/c they are signed
on some platforms and unsigned on others.
................
r61788 | georg.brandl | 2008-03-23 09:05:30 +0100 (Sun, 23 Mar 2008) | 2 lines
Make the doctests presentation-friendlier.
................
r61793 | amaury.forgeotdarc | 2008-03-23 10:55:29 +0100 (Sun, 23 Mar 2008) | 4 lines
#1477: ur'\U0010FFFF' raised in narrow unicode builds.
Corrected the raw-unicode-escape codec to use UTF-16 surrogates in
this case, just like the unicode-escape codec.
................
r61796 | raymond.hettinger | 2008-03-23 14:32:32 +0100 (Sun, 23 Mar 2008) | 1 line
Issue 1681432: Add triangular distribution the random module.
................
r61807 | raymond.hettinger | 2008-03-23 20:37:53 +0100 (Sun, 23 Mar 2008) | 4 lines
Adopt Nick's suggestion for useful default arguments.
Clean-up floating point issues by adding true division and float constants.
................
r61813 | gregory.p.smith | 2008-03-23 22:04:43 +0100 (Sun, 23 Mar 2008) | 6 lines
Fix gzip to deal with CRC's being signed values in Python 2.x properly and to
read 32bit values as unsigned to start with rather than applying signedness
fixups allover the place afterwards.
This hopefully fixes the test_tarfile failure on the alpha/tru64 buildbot.
................
svn+ssh://pythondev@svn.python.org/python/trunk
........
r60752 | mark.dickinson | 2008-02-12 22:31:59 +0100 (Tue, 12 Feb 2008) | 5 lines
Implementation of Fraction.limit_denominator.
Remove Fraction.to_continued_fraction and
Fraction.from_continued_fraction
........
r60754 | mark.dickinson | 2008-02-12 22:40:53 +0100 (Tue, 12 Feb 2008) | 3 lines
Revert change in r60712: turn alternate constructors back into
classmethods instead of staticmethods.
........
r60755 | mark.dickinson | 2008-02-12 22:46:54 +0100 (Tue, 12 Feb 2008) | 4 lines
Replace R=fractions.Fraction with F=fractions.Fraction in
test_fractions.py. This should have been part of the name
change from Rational to Fraction.
........
r60758 | georg.brandl | 2008-02-13 08:20:22 +0100 (Wed, 13 Feb 2008) | 3 lines
#2063: correct order of utime and stime in os.times()
result on Windows.
........
r60762 | jeffrey.yasskin | 2008-02-13 18:58:04 +0100 (Wed, 13 Feb 2008) | 7 lines
Working on issue #1762: Brought
./python.exe -m timeit -s 'from fractions import Fraction; f = Fraction(3, 2)' 'isinstance(3, Fraction); isinstance(f, Fraction)'
from 12.3 usec/loop to 3.44 usec/loop and
./python.exe -m timeit -s 'from fractions import Fraction' 'Fraction(3, 2)'
from 48.8 usec to 23.6 usec by avoiding genexps and sets in __instancecheck__
and inlining the common case from __subclasscheck__.
........
r60765 | brett.cannon | 2008-02-13 20:15:44 +0100 (Wed, 13 Feb 2008) | 5 lines
Fix --enable-universalsdk and its comment line so that zsh's flag completion
works.
Thanks to Jeroen Ruigrok van der Werven for the fix.
........
r60771 | kurt.kaiser | 2008-02-14 01:08:55 +0100 (Thu, 14 Feb 2008) | 2 lines
Bring NEWS.txt up to date from check-in msgs.
........
r60772 | raymond.hettinger | 2008-02-14 02:08:02 +0100 (Thu, 14 Feb 2008) | 3 lines
Update notes on Decimal.
........
r60773 | raymond.hettinger | 2008-02-14 03:41:22 +0100 (Thu, 14 Feb 2008) | 1 line
Fix decimal repr which should have used single quotes like other reprs.
........
r60785 | jeffrey.yasskin | 2008-02-14 07:12:24 +0100 (Thu, 14 Feb 2008) | 11 lines
Performance optimizations on Fraction's constructor.
./python.exe -m timeit -s 'from fractions import Fraction' 'Fraction(3)`
31.7 usec/loop -> 9.2 usec/loop
./python.exe -m timeit -s 'from fractions import Fraction' 'Fraction(3, 2)'`
27.7 usec/loop -> 9.32 usec/loop
./python.exe -m timeit -s 'from fractions import Fraction; f = Fraction(3, 2)' 'Fraction(f)'
31.9 usec/loop -> 14.3 usec/loop
........
r60786 | jeffrey.yasskin | 2008-02-14 08:49:25 +0100 (Thu, 14 Feb 2008) | 5 lines
Change simple instances (in Fraction) of self.numerator and self.denominator to
self._numerator and self._denominator. This speeds abs() up from 12.2us to
10.8us and trunc() from 2.07us to 1.11us. This doesn't change _add and friends
because they're more complicated.
........
Serhiy Storchaka
Ville Skyttä
Ned Batchelder
Mark Dickinson
Sergey B Kirpichev
Furkan Onder
Shantanu
Hugo van Kemenade
Raymond Hettinger
Alex Waygood
Mark Dickinson
Victor Stinner
Terry Jan Reedy
Martin Panter
Larry Hastings
Éric Araujo
Senthil Kumaran
Ezio Melotti
Raymond Hettinger
Georg Brandl
Benjamin Peterson
Christian Heimes