I have a problem with my piece of code in order to get subtotals in sale orders :

[CODE]

import openerp
from openerp import fields, api
from openerp.models import Model
from openerp import _

class tax_line(Model):
    _name = "sale.order.line"
    _inherit = "sale.order.line"

    tax_price = fields.Float(compute='_compute')
    taxed_price = fields.Float(compute='_compute')
    tax_line = fields.Float(compute='_compute')
    taxed_line = fields.Float(compute='_compute')

    @api.multi
    @api.depends('product_uom_qty', 'price_unit', 'price_subtotal', 'product_id', 'tax_id', 'order_id.partner_id', 'discount')
    def _compute(self):
        price = self.price_unit * (1 + (self.discount or 0.0)) / 100.0
        self.tax_price = self.env["account.tax"].compute_all(self.tax_id, price, self.product_uom_qty, self.product_id, self.order_id.partner_id)['taxes']
        self.taxed_price = 0.0
        self.tax_line = 0.0
        self.taxed_line = 0.0

[/CODE]

[CODE]  File "/opt/odoo80/odoo80-server/openerp/fields.py", line 751, in __get__
    self.determine_value(record)
  File "/opt/odoo80/odoo80-server/openerp/fields.py", line 855, in determine_value
    self.compute_value(recs)
  File "/opt/odoo80/odoo80-server/openerp/fields.py", line 811, in compute_value
    self._compute_value(records)
  File "/opt/odoo80/odoo80-server/openerp/fields.py", line 803, in _compute_value
    self.compute(records)
  File "/opt/odoo80/odoo80-server/openerp/api.py", line 235, in wrapper
    return new_api(self, *args, **kwargs)
  File "/opt/odoo80/custom/addons/tax_line/tax_line.py", line 27, in _compute
    self.tax_price = self.env["account.tax"].compute_all(self.tax_id, price, self.product_uom_qty, self.product_id, self.order_id.partner_id)['taxes']
  File "/opt/odoo80/odoo80-server/openerp/api.py", line 235, in wrapper
    return new_api(self, *args, **kwargs)
  File "/opt/odoo80/odoo80-server/addons/account/account.py", line 2120, in compute_all
    product=product, partner=partner, force_excluded=force_excluded)
  File "/opt/odoo80/odoo80-server/openerp/api.py", line 237, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo80/odoo80-server/addons/account/account.py", line 2091, in compute_all
    totalin = totalex = round(price_unit * quantity, precision)
QWebException: ""unsupported operand type(s) for *: 'account.tax' and 'float'" while evaluating
'l.tax_price'" while evaluating
"translate_doc(doc_id, doc_model, 'partner_id.lang', 'sale.report_saleorder_document')"[/CODE]

My XML Report just implement the new fields and there is no problem if i do something in my .py code like self.tax_price = self.price_unit

Thanks for your help!