BOM继承字段精度问题

[xiaobaixy]

from openerp.osv import osv, fields<br />import openerp.addons.decimal_precision as dp<br /><br />class mrp_bom(osv.osv):<br />&nbsp; &nbsp; _inherit = &#039;mrp.bom&#039;<br />&nbsp; &nbsp; _columns = {<br />&nbsp; &nbsp;  <br />&nbsp; &nbsp; &nbsp; &nbsp; &#039;cost_price&#039;: fields.related(&#039;product_id&#039;,&#039;cost_price&#039;,type=&#039;float&#039;,digits_compute = dp.get_precision(&#039;Product Price&#039;),relation=&quot;product.product&quot;, string=&quot;Cost Parts Of Bom&quot;, store=False),<br />&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; 

默认mrp.bom字段精度为两位，想通过改精度改不了digits_compute = dp.get_precision('Product Price')

问下这个精度怎么改