Persuading ConfigParser to give me the section elements in the same order as the file

[geoffbache]

Hi Matt,

> Have a look at this:http://www.python.org/dev/peps/pep-0372/
>

Thanks, that was very useful. Good to know these things are being
considered.

> Looking at the config parser module, it looks like there are only a
> couple of places where {} is used. I would create a mixin class to
> replace the offending methods. That should work because it looks like
> you only have to replace "__init__" and "add_section". So...
>
> class OrderedConfigParserMixin:
>     def __init__(self, defaults=None):
>         self._sections = ndict.seqdict()
>         self._defaults = ndict.seqdict()
>         if defaults:
>             for key, value in defaults.items():
>                 self._defaults[self.optionxform(key)] = value
>
>     def add_section(self, section):
>         """Create a new section in the configuration.
>
>         Raise DuplicateSectionError if a section by the specified name
>         already exists.
>         """
>         if section in self._sections:
>             raise DuplicateSectionError(section)
>         self._sections[section] = ndict.seqdict()
>
> # Then you can use this to create your own ordered config parsers.
> Note that
> # multiple inheritance in python uses a breadth first search. If you
> want
> # the methods on your mixin to get called instead of the methods on
> the
> # original class you must include the mixin first.
>
> from ConfigParser import RawConfigParser, ConfigParser,
> SafeConfigParser
>
> class OrderedRawConfigParser(OrderedConfigParserMixin,
> RawConfigParser):
>     pass
>
> class OrderedConfigParser(OrderedConfigParserMixin, ConfigParser):
>     pass
>
> class OrderedSafeConfigParser(OrderedConfigParserMixin,
> SafeConfigParser):
>     pass
>
> I don't know if this is the _best_ approach, but it is certainly much
> preferred over monkey patching the built-ins module. Note that I
> haven't tested any of the above code.

Yes, I tried this first. But actually you missed the main place where
dictionaries are created, which is the monster method _read, the line
being

cursect = {'__name__': sectname}

I thought by the time I'd copied that whole method just to edit that
line I may as well just copy the whole file and forget the
inheritance :)

btw, the PEP you pointed me at indicated ConfigParser will take a
dict_type argument for exactly this purpose in Python 2.6, so I look
forward to when I can use that instead...

Regards,
Geoff