How do I automatically retrieve the data from a field which is already stored in the database so that it can be used the autofill another many2one field which is new ? for example

I have a course_id field which already has Its Stored data in the database

course_id = fields.Many2one ('op.course', 'Course') 

Then i created another new program_id field inside the same class

program_id = fields.Many2one ('op.program', 'Program', domain = "[('course_id', '=', course_id)]")

 When i tried the onchange method, it works perfectly

@ api.onchange ('course_id') 
        def onchange_course (self): 
                    prog_id = false 
                   if self.course_id and self.course_id.program_id: 
                    prog_id = self.course_id.program_id.id 
                    self.program_id = prog_id 

But now i want program_id field to be updated automatically in the tree and form view  by using the course ids which are already stored. Am using Odoo version 12