How to raise an error when open a window ODOO?

Question

I would like to know how to raise an error when I open a window in Odoo.
For example, I open Sales window, and it'll raise an error or warning like "Hello" or anything else.

I know to use exception like:

from openerp.osv import osv,fields
from openerp.tools.translate import _
from openerp import pooler
from openerp.exceptions import except_orm`

raise osv.except_osv(_('Hello'), _('Hello World'))

but I don't know where should I put the code to raise that.

Answer 1

1. Use default_get method, It will execute whenever click on the CREATE button.

2. Add a field in list/form view as compute field, and add raise osv.except_osv(_('Hello'), _('Hello World')) in compute function.

3. For a button action. define a function and call it in button definition.

   <button name='function_name' type='object'/>