Using default traitlet values from the Javascript side

[psychemedia]

When setting initial values for traitlets / shared state across the python and js sides, the initial/default value seems to inherit from the pyhton side.

Is there a simple way of allowing the initial state to be set from the Javascript side?

[manzt]

The Python model definition is the source of truth. JavaScript must be loaded and executed to set a value on the Python side. One option would be to allow_none on the trait and set the value if undefined within the initialize lifecycle hook.

However, I don't recommend this approach because there will be timing issues where a property is None on the Python side if it is never set by JS.

[psychemedia]

Ok - thanks.

FWIW, my use case is running a simulator in the widget. The Python sid sends code to the siimulator, the simulator widget executes it, and then the js simulator exposes some state back for analysis.