Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder1.enfer-du-nord.net!feeder.news-service.com!newsfeed.xs4all.nl!newsfeed5.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
To: python-list@python.org
From: Lie Ryan <lie.1296@gmail.com>
Subject: Re: Dynamically creating properties?
Date: Fri, 28 Oct 2011 14:42:34 +1100
References: <a47fb589-520a-49ec-9864-cac1d7ea11eb@s9g2000yqi.googlegroups.com> <b955b690-8045-4de1-b0dd-dcf0a05cc92f@v5g2000vbh.googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1
In-Reply-To: <b955b690-8045-4de1-b0dd-dcf0a05cc92f@v5g2000vbh.googlegroups.com>
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.2274.1319773376.27778.python-list@python.org>
Lines: 73
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:15085

On 10/28/2011 08:48 AM, DevPlayer wrote:
> On Oct 27, 3:59 pm, Andy Dingley<ding...@codesmiths.com>  wrote:
>> I have some XML, with a variable and somewhat unknown structure. I'd
>> like to encapsulate this in a Python class and expose the text of the
>> elements within as properties.
>>
>> How can I dynamically generate properties (or methods) and add them to
>> my class?  I can easily produce a dictionary of the required element
>> names and their text values, but how do I create new properties at run
>> time?
>>
>> Thanks,
>
>      class MyX(object):
>          pass
>      myx = myx()
>
>      xml_tag = parse( file.readline() )
>
>      # should be a valid python named-reference syntax,
>      # although any object that can be a valid dict key is allowed.
>      # generally valid python named reference would be the answer to
> your question
>      attribute = validate( xml_tag )
>
>      # dynamicly named property
>      setattr( myx, attribute, property(get_func, set_func, del_func,
> attr_doc) )
>
>      # "dynamicly named method"
>      # really should be a valid python named-reference syntax
>      myfunc_name = validate(myfunc_name)
>
>      def somefunc(x):
>          return x+x
>      # or
>      somefunc = lambda x: x + x
>
>      setattr( myx, myfunc_name, somefunc )
>
>
> So beaware of:
>      # \\\\\\\\\\\\\\\\\\\\\\\\\
>      setattr(myx, '1', 'one')
>
>      myx.1
>          File "<input>", line 1
>          x.1
>            ^
>      SyntaxError: invalid syntax
>
>      # \\\\\\\\\\\\\\\\\\\\\\\\\
>      x.'1'
>        File "<input>", line 1
>          x.'1'
>              ^
>      SyntaxError: invalid syntax
>
>      # \\\\\\\\\\\\\\\\\\\\\\\\\
>      x.__dict__['1']   # returns
>      'one'
>
>      x.__dict__        # returns
>      {'1': 'one'}
>
> So you should validate your variable names if you are getting them
> from somewhere.

XML does not allow attribute names to start with a number, so I doubt 
you need to worry about that. In addition, if you also need to 
dynamically access attributes and you have zero control of the name, you 
can use getattr().