[Python-Dev] Interest in integrating C decimal module into Python?

Tue Oct 20 23:00:12 CEST 2009

2009年10月20日 Stefan Krah <stefan-usenet at bytereef.org>:
> Hi,
>> as some of you know, recently I've released an arbitrary precision
> C library for decimal arithmetic together with a Python module:
>> http://www.bytereef.org/libmpdec.html
> http://www.bytereef.org/fastdec.html
>>> Both the library and the module have been tested extensively. Fastdec
> currently differs from decimal.py in a couple of ways that could be
> fixed. The license is AGPL, but if there is interest in integrating it
> into Python I'd release it under a Python-compatible license.
>>> There have been several approaches towards getting C decimal arithmetic
> into Python:
>> http://bugs.python.org/issue2486
>>> Fastdec follows Raymond Hettinger's suggestion to provide wrappers for
> an independent C implementation. Arguments in favour of fastdec are:
>>  * Complete implementation of Mike Cowlishaw's specification
>>  * C library can be tested independently
>>  * Redundant arithmetic module for tests against decimal.py
>>  * Faster than Java BigDecimal
>>  * Compares relatively well in speed against gmpy
>>> To be clear, I would not want to _replace_ decimal.py. Rather I'd like to
> see a cdecimal module alongside decimal.py.

Why? If it's 100% compatible with decimal.py, just replace it. All the
user should see is improved speed. Let's not do another
pickle/cpickle.
> I know that ultimately there should be a PEP for module inclusions. The
> purpose of this post is to gauge interest. Specifically:
>>> 1. Are you generally in favour of a C decimal module in Python?

Yes, although I have to admit my interest is fairly theoretical.
> 2. Would fastdec - after achieving full decimal.py compatibility - be
>   a serious candidate?

I don't see why not, if it was 100% compatible with decimal.py
> 3. Could I use this list to settle a couple of questions, or would perhaps
>   a Python developer be willing to work with me to make it compatible? I'm
>   asking this to avoid doing work that would not find acceptance afterwards.

I can't help much here, but I'd prefer to see discussions on
python-dev so I'm +1 on keeping discussions here.
Waiting eagerly to hear the experts' comments...
Paul.