purchase_update_prices_cost/purchase.py

# -*- encoding: utf-8 -*-

from openerp import  models, fields
from datetime import date

class account_invoice(models.Model):
    _inherit = 'account.invoice'

    def invoice_validate(self):
        res = super(account_invoice, self).invoice_validate()
        for item in self.invoice_line:
            if item.purchase_line_id:
                product = self.env['product.product'].browse(item.product_id.id)
                if product:
                    template = self.env['product.template'].browse(product.product_tmpl_id.id)
                    if(template.price_change == 'purchase'):
                        product.write({'standard_price': item.price_unit, 'last_purchase_date': date.today()})
                    else:
                        product.write({'last_purchase_date': date.today()})
        return res