Path: csiph.com!eeepc.pasdenom.info!news.pasdenom.info!news.dougwise.org!gegeweb.org!de-l.enfer-du-nord.net!feeder2.enfer-du-nord.net!feeds.phibee-telecom.net!newsfeed.xs4all.nl!newsfeed5.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
MIME-Version: 1.0
In-Reply-To: <AANLkTimw6N7vDtc4zoEw5TRznCeR1e0yGydz4AKiLM3E@mail.gmail.com>
References: <8e0efff7-4d38-4a85-9653-2178388603d4@y36g2000pra.googlegroups.com> <87oc6l8z1y.fsf@rudin.co.uk> <c2cb4f8c-909e-4e47-b610-6d935c0c2ca1@w19g2000yqa.googlegroups.com> <AANLkTinsi3zGvcZSQySA3z1qZPn_tiT3q8BEBrErRpcZ@mail.gmail.com> <4D53166D.6050103@mrabarnett.plus.com> <AANLkTimw6N7vDtc4zoEw5TRznCeR1e0yGydz4AKiLM3E@mail.gmail.com>
Date: Thu, 10 Feb 2011 03:31:41 -0500
Subject: Re: Easy function, please help.
From: Benjamin Kaplan <benjamin.kaplan@case.edu>
To: python-list@python.org
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.71.1297326713.1633.python-list@python.org>
Lines: 60
NNTP-Posting-Host: 82.94.164.166
Xref: csiph.com comp.lang.python:55776

On Thu, Feb 10, 2011 at 12:03 AM, Jason Swails <jason.swails@gmail.com> wro=
te:
>
>
> On Wed, Feb 9, 2011 at 5:34 PM, MRAB <python@mrabarnett.plus.com> wrote:
>>
>> On 09/02/2011 21:42, Jason Swails wrote:
>>>
>>> You've gotten several good explanations, mainly saying that 0 -> False
>>> and not 0 -> True, which is why the while loop exits. =A0You've also
>>> gotten advice about how to make your method more robust (i.e. force
>>> integer division).
>>>
>>> However, as surprising as this may be I'm actually with RR on this one
>>> (for a little) -- for code readability's sake, you should make your
>>> conditional more readable (i.e. don't depend on the fact that the
>>> iterations will take your test value down to 0 which conveniently in
>>> this case evaluates to False). =A0This could encourage you in later cas=
es
>>> to think that if this result eventually converged to a different number=
,
>>> say the multiplicative identity instead, that the same approach will
>>> work (when instead it'll dump you into an infinite loop).
>>>
>>> You've also gotten the suggestion of typecasting to a string and then
>>> looking at the number of characters in the string. =A0This works fine f=
or
>>> integers and positive numbers, but not so well for negatives and floats=
,
>>> since both the decimal and negative sign will be counted. =A0You could
>>> typecast to a string then strip out '-' and '.' and then count the
>>> characters. =A0i.e.
>>>
>>> def num_digits(n):
>>> =A0 =A0return len(str(n).replace('-','').replace('.',''))
>>>
>> Or:
>>
>> def num_digits(n):
>> =A0 =A0return len(str(abs(n)).replace('.',''))
>>
>>> Or typecast to an int if you want to neglect decimals before converting
>>> to a string, etc.
>>>
>> [snip]
>> Python doesn't have typecasting. :-)
>
> Because these basic types are not mutable?=A0 <excuse> Most of my work ha=
s to
> be in Fortran, so I'm a relative newcomer to Python.=A0 When I don't need
> Fortran-y performance it's much nicer (obviously to anyone that's used th=
em
> both)!=A0 Still don't know much deeper than Python's cosmetic surface at =
this
> point. </excuse>
>

Not exactly. It's because everything in Python is an object. What
you're doing isn't type casting. It's just calling an object
constructor- no different than any other class in the language.