Task: Update a configuration file







Python: 




import re
import string





DISABLED_PREFIX = ';'





class Option(object):
    

    
    def __init__(self, name, value=None, disabled=False,
                 disabled_prefix=DISABLED_PREFIX):
        
        self.name = str(name)
        self.value = value
        self.disabled = bool(disabled)
        self.disabled_prefix = disabled_prefix

    
    def __str__(self):
        
        disabled = ('', '%s ' % self.disabled_prefix)[self.disabled]
        value = (' %s' % self.value, '')[self.value is None]
        return ''.join((disabled, self.name, value))

    
    def get(self):
        
        enabled = not bool(self.disabled)
        if self.value is None:
            value = enabled
        else:
            value = enabled and self.value
        return value

    



class Config(object):
    
    
    reOPTION = r'^\s*(?P<disabled>%s*)\s*(?P<name>\w+)(?:\s+(?P<value>.+?))?\s*$'

    
    def __init__(self, fname=None, disabled_prefix=DISABLED_PREFIX):
        
        self.disabled_prefix = disabled_prefix
        self.contents = []          
        self.options = {}           
        self.creOPTION = re.compile(self.reOPTION % self.disabled_prefix)
        if fname:
            self.parse_file(fname)

    
    def __str__(self):
        
        return '\n'.join(map(str, self.contents))

    
    def parse_file(self, fname):
        
        with open(fname) as f:
            self.parse_lines(f)
        return self

    
    def parse_lines(self, lines):
        
        for line in lines:
            self.parse_line(line)
        return self

    
    def parse_line(self, line):
        
        s = ''.join(c for c in line.strip() if c in string.printable) 
        moOPTION = self.creOPTION.match(s)
        if moOPTION:
            name = moOPTION.group('name').upper()
            if not name in self.options:
                self.add_option(name, moOPTION.group('value'),
                                moOPTION.group('disabled'))
        else:
            if not s.startswith(self.disabled_prefix):
                self.contents.append(line.rstrip())
        return self

    
    def add_option(self, name, value=None, disabled=False):
        
        name = name.upper()
        opt = Option(name, value, disabled)
        self.options[name] = opt
        self.contents.append(opt)
        return opt

    
    def set_option(self, name, value=None, disabled=False):
        
        name = name.upper()
        opt = self.options.get(name)
        if opt:
            opt.value = value
            opt.disabled = disabled
        else:
            opt = self.add_option(name, value, disabled)
        return opt

    
    def enable_option(self, name, value=None):
        
        return self.set_option(name, value, False)

    
    def disable_option(self, name, value=None):
        
        return self.set_option(name, value, True)

    
    def get_option(self, name):
        
        opt = self.options.get(name.upper())
        value = opt.get() if opt else None
        return value





if __name__ == '__main__':
    import sys
    cfg = Config(sys.argv[1] if len(sys.argv) > 1 else None)
    cfg.disable_option('needspeeling')
    cfg.enable_option('seedsremoved')
    cfg.enable_option('numberofbananas', 1024)
    cfg.enable_option('numberofstrawberries', 62000)
    print cfg