class EventHandler:
    """Calls the set of functions that handle a given event.

    You don't need to register events. You can EventHandler.handle('whatever')
    """
    #A tuple so that unbind and emit won't crash
    #bind will make it a dictionary, making it useful
    _eventBindings = ()
    def register(self, *events):
        if type(self._eventBindings) is tuple:
            self._eventBindings = {}
        for event in events:
            self._eventBindings[event] = set()

    def bind(self, event, function):
        assert event in self._eventBindings
        self._eventBindings[event].add(function)

    def unbind(self, event, function):
        assert event in self._eventBindings
        if function in self._eventBindings[event]:
            self._eventBindings[event].remove(function)

    def emit(self, event, *args):
        assert event in self._eventBindings
        for function in self._eventBindings[event]:
            function(*args)

    def __repr__(self):
        return '<EventHandler instance binding %s>' %str(self._eventBindings)