ConfigParser reads capital keys and make them lower case

I found one interesting observation. I had written one config file read program as,

import ConfigParser
class  ConfReader(object):
    ConfMap = dict()

    def __init__(self):
        self.config = ConfigParser.ConfigParser()
        self.config.read('./Config.ini')
        self.__loadConfigMap()

    def __loadConfigMap(self):
        for sec in self.config.sections():
            for key,value in self.config.items(sec):
                print 'key = ', key, 'Value = ', value
                keyDict = str(sec) + '_' + str(key)
                print 'keyDict = ' + keyDict  
                self.ConfMap[keyDict] = value

    def getValue(self, key):
        value = ''
        try:
            print ' Key = ', key
            value = self.ConfMap[key] 
        except KeyError as KE:
            print 'Key', KE , ' didn\'t found in configuration.'
    return value

class MyConfReader(object):
    objConfReader = ConfReader()

def main():
     print MyConfReader().objConfReader.getValue('DB2.poolsize')
     print MyConfReader().objConfReader.getValue('DB_NAME')

if __name__=='__main__':
    main()

And my Config.ini file looks like,

[DB]
HOST_NAME=localhost
NAME=temp
USER_NAME=postgres
PASSWORD=mandy

The __loadConfigMap() works just fine. But while reading the key and values, it is making the keys lower case. I didn't understand the reason. Can any one please explain why it is so?

Solution

ConfigParser.ConfigParser() is documented to behave this way, in the Mapping Protocol Access section:

By default, all keys in sections are accessible in a case-insensitive manner. E.g. for option in parser["section"] yields only optionxform’ed option key names. This means lowercased keys by default.

That's because this module parses Windows INI files which are expected to be parsed case-insensitively.

You can disable this behaviour by replacing the ConfigParser.optionxform() function:

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

str passes through the options unchanged.