Command abstraction

class CommandError (Exception):
    """Represents an error on command handling"""
    pass

class Command (object):
    """Command

    Represents a command executed from CLI or
    the daemon.
    """
    _data = {}
    def __init__(self, command, params=None):
        """Constructor"""
        self._data['command'] = command.lower()
        if params is not None:
            self._data['params'] = dict(params)
        else:
            self._data['params'] = {}

    def get_command(self):
        """Returns the command name"""
        return self._data['command']

    def __getattr__(self, attr):
        return self._data[attr]

    def __setattr__(self, attr, value):
        self._data[attr] = value
        return self

   def __unicode__(self):
       """Returns the name of the command"""
       return self._data['command']


class CommandHandler (object):
    """Command handler

    Handles commands and parameters supplied
    by users and makes the appropriate calls
    to the API.
    """
    _api = None
    def __init__ (self):
        """Constructor"""
        self._api = API()

    def handle (self, command):
        """Handles a command and outputs the response"""
        if not isinstance(command, Command):
            raise CommandError("Invalid command. Expecting Command object")

        cmd = command.get_command()
        if callable(getattr(self._api, cmd)):
            pass
        else:
            raise CommandError("Invalid command %s" % cmd)