Handle first callback on App start

[chriddyp]

@rvsingh011

It’s easy with a button but it get harder with other components. I want to know the best way I can handle this for a lot of callbacks.

Checking if the property is None should work for all properties (unless you’ve initialized them to something different). You can also prevent updates by raising dash.exceptions.PreventUpdate().

So, your code would be like:

if value is None:
   raise dash.exceptions.PreventUpdate()