Total amount in words in qweb report odoo

I want to get total amount of purchase order in words on qweb report. Someone please tell me what is the process to get it or what code i can do... i'll be very thankful...

Create a function in your purshase.order model that converts total_amount to letters.

from openerp import models, api
from openerp.tools import amount_to_text_en

class purchase_order(models.Model):
    _inherit = 'purchase.order'

    @api.depends('amount_total', 'currency_id')
    def compute_text(self):
        return amount_to_text_en.amount_to_text(self.amount_total, self.currency_id.symbol)

To call it from QWEB reports use:

<span t-esc="o.compute_text()" />