What is the use of app_data in callback ??

[pbk0]

@hoffstadt @Pcothren
I refered to documentation here, but fail to understand use of app_data kwarg. I looked in demo.py and what I assume is that app_data only provides the value of the sender. But in that case I can just extract that info from sender itself i.e. using dpg.get_value(sender) and there will be no need for app_data kwarg.

Look at below code. I assume that this assert will never fail ... is my assumptions valid ???

I feel that there is more to app_data than what I think in that case please explain or provide refrences. Thanks in advance :)

def callback_fn(sender, app_data, user_data):
    assert dpg.get_value(sender) == app_data, "I assume that this assert will never fail"