Preserve case in ConfigParser?

Question

I have tried to use Python's ConfigParser module to save settings. For my app it's important that I preserve the case of each name in my sections. The docs mention that passing str() to ConfigParser.optionxform() would accomplish this, but it doesn't work for me. The names are all lowercase. Am I missing something?

<~/.myrc contents>
[rules]
Monkey = foo
Ferret = baz

Python pseudocode of what I get:

import ConfigParser,os

def get_config():
   config = ConfigParser.ConfigParser()
   config.optionxform(str())
    try:
        config.read(os.path.expanduser('~/.myrc'))
        return config
    except Exception, e:
        log.error(e)

c = get_config()  
print c.options('rules')
[('monkey', 'foo'), ('ferret', 'baz')]

Answer 1

Caveat:

If you use defaults with ConfigParser, i.e.:

config = ConfigParser.SafeConfigParser({'FOO_BAZ': 'bar'})

and then try to make the parser case-sensitive by using this:

config.optionxform = str

all your options from config file(s) will keep their case, but FOO_BAZ will be converted to lowercase.

To have defaults also keep their case, use subclassing like in @icedtrees answer:

class CaseConfigParser(ConfigParser.SafeConfigParser):
    def optionxform(self, optionstr):
        return optionstr

config = CaseConfigParser({'FOO_BAZ': 'bar'})

Now FOO_BAZ will keep it's case and you won't have InterpolationMissingOptionError.

Answer 2

The documentation is confusing. What they mean is this:

import ConfigParser, os
def get_config():
    config = ConfigParser.ConfigParser()
    config.optionxform=str
    try:
        config.read(os.path.expanduser('~/.myrc'))
        return config
    except Exception, e:
        log.error(e)

c = get_config()  
print c.options('rules')

I.e. override optionxform, instead of calling it; overriding can be done in a subclass or in the instance. When overriding, set it to a function (rather than the result of calling a function).

I have now reported this as a bug, and it has since been fixed.

Answer 3

For me worked to set optionxform immediately after creating the object

config = ConfigParser.RawConfigParser()
config.optionxform = str 

Answer 4

Add to your code:

config.optionxform = lambda option: option  # preserve case for letters

Answer 5

I know this question is answered, but I thought some people might find this solution useful. This is a class that can easily replace the existing ConfigParser class.

Edited to incorporate @OozeMeister's suggestion:

class CaseConfigParser(ConfigParser):
    def optionxform(self, optionstr):
        return optionstr

Usage is the same as normal ConfigParser.

parser = CaseConfigParser()
parser.read(something)

This is so you avoid having to set optionxform every time you make a new ConfigParser, which is kind of tedious.