Path: csiph.com!usenet.pasdenom.info!aioe.org!news.stack.nl!newsfeed.xs4all.nl!newsfeed2.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
Return-Path: <ian.g.kelly@gmail.com>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.044
X-Spam-Evidence: '*H*': 0.92; '*S*': 0.01; 'context': 0.07; 'exp': 0.09; 'def': 0.12; '24,': 0.16; 'although,': 0.16; 'decimal.': 0.16; 'str()': 0.16; 'sat,': 0.16; 'wrote:': 0.18; 'aug': 0.22; 'handling': 0.26; 'subject:/': 0.26; 'header:In-Reply-To:1': 0.27; 'function': 0.29; 'am,': 0.29; 'message-id:@mail.gmail.com': 0.30; 'decimal': 0.31; 'subject:numbers': 0.31; 'guess': 0.33; 'skip:d 20': 0.34; 'received:google.com': 0.35; 'version': 0.36; 'to:addr :python-list': 0.38; 'sure': 0.39; 'to:addr:python.org': 0.39; 'ian': 0.60; '50%': 0.78; 'subject:Fast': 0.84; 'careful': 0.91; '2013': 0.98
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type; bh=icpTMIRMN6vOD2uIWDuYSAEIRHPTc4bQZcqF45gPDGw=; b=vkxbnmPzKXn/+pcoEoWTtA7jNYzN51HjFQHmhE9IQT8wx1hyT7+GztJbh0Qwlixw9n vmCooWG7skCoKbQW4vgYe6fKkErrqoxj+yd2MtU2fhDnGI8j9OnzylaPlHuKq140MBui FQ8rclGs1fKmLFZWODoXzYVQYKW72clU4jZ9GitfeWL5f2e3yqlSE1ihKkadvOkr+Y3r p1QErdRYxD0A5z5Fc2ivUTFWHOv/MJuX/D7XTOd6QoePn1wVcHFHR+4X02wHd1UzqG73 NRq0Ab4eq+En1dDtVN06JcxpStv3Wrvn+KuayrzvDxbWyggtwWazNnPGGa0MuQrq4SD/ AI2g==
X-Received: by 10.68.178.35 with SMTP id cv3mr3830594pbc.160.1377330648700; Sat, 24 Aug 2013 00:50:48 -0700 (PDT)
MIME-Version: 1.0
In-Reply-To: <CALwzidm5km=wzMJn4RoR9hcnSOUqyyq-BWo89owMHBGwTyztLA@mail.gmail.com>
References: <521828e7$0$29986$c3e8da3$5496439d@news.astraweb.com> <CALwzidm5km=wzMJn4RoR9hcnSOUqyyq-BWo89owMHBGwTyztLA@mail.gmail.com>
From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Sat, 24 Aug 2013 01:50:08 -0600
Subject: Re: Fast conversion of numbers to numerator/denominator pairs
To: Python <python-list@python.org>
Content-Type: text/plain; charset=ISO-8859-1
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <http://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list/>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <http://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.191.1377330651.19984.python-list@python.org>
Lines: 14
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1377330651 news.xs4all.nl 15869 [2001:888:2000:d::a6]:55070
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:52931

On Sat, Aug 24, 2013 at 1:37 AM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
>
> I time this function at about 33% faster than your version for a
> six-digit decimal, and almost 50% faster for a 12-digit decimal.  My
> guess would be because it's not calling str() on every individual
> digit.
>
> def convert(d):
>     exp = d.as_tuple().exponent
>     num = int(d.scaleb(-exp))
>     return num, 10**-exp

Although, you would need to be careful with handling the decimal
context for the scaleb operation to make sure the result is exact.