i want to create a user using my custom module, for i am inheriting res.users and res.partners in my custom module but nothing happens it gives me error

Here is the code

class tact_customer(osv.osv):

_name = 'tact.customer'

_inherit =['res.partner','res.users']

_columns = {

'longitude': fields.char('Longitude',size=40,required=True, help='longitude'),

'latitude': fields.char('Latitude',size=40,required=True, help='latitude'),

}

customer()