Restore "Link to Default" property values by Python

[_c_]

I am trying to set elements' values to their defaults: be it undefined, expression, or value. Whatever is in the Attribute Manager for the property definition. For clarifying, by default will look like this upon selection:

default undefined value	default defined value	default expression

There is no direct access in the JSON API, but I found a trick to determine if a property is defined by expression: they DON'T have a "defaultValue" dict key.

It seems nevertheless to be impossible to actually SET the property value to "Link to Default". Whenever I copy the defaults from the property definition into the element's value this turns into "custom".

Does anyone know a trick?

[_c_]

I'd like to put this thread into the praxis context it came from.

I was working on a door list with odd 1800 items when I realised that a large number of elements had an override of "from/to room number" calculated properties into a fixed custom value. It came from ill prepared favourites.

This could have been a fatal error.

It is important to fish out elements whose calculations are overridden and possibly set them by script.