Thank you very much for your answers. I guess there is no way to know the id of the object that will be used to edit in this form.

Hi,

fields_view_get() method will be called whenever you clicked your form view.

This is a sample:

def fields_view_get(self, cr, uid, view_id=None, view_type='form', context=None, toolbar=False, submenu=False):

     res = super(class_name, self).fields_view_get(cr, uid, view_id, view_type, context=context, toolbar=toolbar)

     #your modification

     return res

Hi,

If you want to do something while opening a form view, you may either override the fields_view_get() method or you may go for a functional field. 

Overriding the fields_view_get() method would be better, and you may find some example references in Odoo addons folder.

Refer this link also: 

http://stackoverflow.com/questions/33654347/how-to-use-fields-view-get-in-odoo-8