I am trying to replicate the behaviour of the sales order line items.  What I would like to do is this.

When the user selects a product from the drop down that is linked back to the product part number, copy the description field for that product into the description field on the line item.  I don't want to use  a related field because sometime the description might have to be customized.

I am trying to do this with python code in an automated action but I'm new to this and am confused on how to get a value from a field in another model.

I am using the SaaS version of Odoo.

Trigger Condition = Based on form modification

onChange fields trigger = x_part_num

I've tried several things in my python code but to no avail.  I'm trying to do something like this

record['x_description'] = partModel.description   (obviously this is just pseudo code as an example of what i'm trying to achieve).

Any mentoring and advice is appreciated.