Display value on a field if another field is being changed/set before saving form

[Testing_tryton]

Hello, can someone tell how to trigger a change in one field when another field is modified in Tryton, specifically before the record is saved (on the form, during the user interaction).
Thank you

[dave (David Harper)]

You should be able to use on_change and on_change_with methods to do this: Fields — Tryton server

Here is an example in the sale module that updates various fields when the product on a line is changed: modules/sale/sale.py · bb3c526ac15a1498f679408acbab97905ae265a5 · Tryton / Tryton · GitLab