You can use any of the provided Options here but the final adjustment is that you need to set the widget selection for the field in your xml view definition. For example:

#in your .py  

_columns = {

    'partner_sup_id': fields.many2one('res.partner', 'Select Supplier 2 ', domain=[('supplier','=',True), ('is_company','=',True)),

}

#in your xml
 

<field name="partner_sup_id" widget="selection">
 

Well if you don't want to use Domain / Widget...

Then you can try with either of these options

Option 1:

Define a field as Selection, instead of Many2One, along with a selection to achieve your requirement...

Coming to your Requirement:

def _get_partner_sup(self, cr, uid, context=None):

obj = self.pool.get('res.partner')

ids = obj.search(cr, uid, [('supplier','=',True), ('is_company','=',True)])

res = obj.read(cr, uid, ids, ['name', 'id','email'], context)

res = [(r['id'], r['name']) for r in res]

return res

_columns = {

'partner_sup_id': fields.Selection(selection=_get_partner_sup),

}

Option2: If your intention is just not to provide Create/Edit option to the users, then in XML, against that fields just "options={'no_create':True}", by doing this also, you can achieve the same...