title: How to set computed one2many field calculation odoo
body: <p>I just want to know how to set the values in one2many by using computed field calculation. Here my code is</p>
  
  <p>python file</p>
  
  <pre><code>from openerp import models ,fields,api
  from openerp import SUPERUSER_ID
  from dateutil.relativedelta import relativedelta
  import openerp.addons.decimal_precision as dp
  import math
  import logging
  import datetime
  
  class extend_product_product(models.Model):
      _inherit = 'product.product'
  
      monthly_lines = fields.One2many('minmax.monthly.data','month_id', 'Monthy Sales',compute="_get_monthly_sales")
  
   @api.one
   def _get_monthly_sales(self):
      vals = {}
      vals.update({'monthly_lines':[(0,0,{'month_name_id':1,'so_qty':35})]})
      self.write(vals) # Also I have tried self.monthly_lines = [(0,0,{'month_name_id':1,'so_qty':35})]
  
  class minmax_monthly_data(models.Model):
      _name = 'minmax.monthly.data'
  
      month_id = fields.Many2one('product.product', 'Product Reference', select=True, required=True)
      month_name_id = fields.Many2one('minmax.months','Minmax Month',required=True)
      so_qty = fields.Float('Sales Qty', digits_compute=dp.get_precision('Product Unit of Measure'), required=True)
  </code></pre>
  
  <p>XML File</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;openerp&gt;
      &lt;data&gt;
        &lt;record model="ir.ui.view" id="product_monthly_minmax_tree"&gt;
              &lt;field name="name"&gt;product.product.tree&lt;/field&gt;
              &lt;field name="model"&gt;product.product&lt;/field&gt;
              &lt;field name="inherit_id" ref="product.product_product_tree_view"/&gt;
              &lt;field name="type"&gt;form&lt;/field&gt;
              &lt;field name="arch" type="xml"&gt;
                  &lt;field name="ean13" position="after"&gt;
                      &lt;field name="monthly_lines" widget="one2many_tags" /&gt;
                  &lt;/field&gt;
              &lt;/field&gt;
          &lt;/record&gt;
      &lt;/data&gt;
  &lt;/openerp&gt;
  </code></pre>
  
  <p>Here I have tried to insert the data manually. The function is called properly whenever we load the product.product tree view. But there is no results. Thanks in advance.</p>