connect_weakly

lass __WeakWrapper(object):
    def __init__(self, sender, callback, *userdata):
        self.weak_obj = weakref.ref(callback.im_self)
        self.weak_fun = weakref.ref(callback.im_func)
        self.userdata = userdata
        self.sender = sender
        self.handle = None

    def __call__(self, source):
        obj = self.weak_obj()
        func = self.weak_fun()
        if obj is not None and func is not None:
            return func(obj, source, self.userdata)
        elif self.handle is not None:
            self.sender.disconnect(self.handle)
            self.handle = None
            self.sender = None


def connect_weakly(sender, signal, callback, *userdata):
    wrapper = __WeakWrapper(sender, callback, userdata)
    wrapper.handle = sender.connect(signal, wrapper)
    return wrapper