class myClass(models.Model):
number_1 = fields.Integer()
number_2 = fields.Integer()
sum = fields.Integer(compute="compute_sum", store=True)
@api.depends('number_1','number_2')
@api.multi
def compute_sum(self):
for record in self:
total = record.number_1 + record.number_2
record.sum = total