I have a problem and is this:

I have a field attachment and I want to read for modify the text.

Any suggestions ?

code:

class contract_type(osv.osv):
     _inherit = 'hr.contract.type'

    _columns = {
        'attachment': fields.many2one('ir.attachment', 'Adjuntar'),
        'dni': fields.char('DNI'),
        'ruc': fields.char('Nro. Ruc'),
        'name_employee': fields.char('Nombre'),
        'address': fields.char('Direccion'),
        'job_position': fields.char('Cargo'),
        'salary': fields.char('Salario'),
        'start_date': fields.date('Fecha de Inicio'),
        'end_date': fields.date('Fecha Fin'),
    }

    _defaults = {
       'start_date': lambda *a: time.strftime('%Y-%m-%d'),
   }

contract_type()