I would like to modify the source code of a module to allow the calculation of a "due date invoices", the topic is to calculate it from the last day of a month.

I modified a file already modified and there is an associated view.xml but I don't know how I can modify this view.

I saved the former code in comment.

my account.py :

from openerp.osv import osv, fields

def compute(self, cr, uid, id, value, context=None):
    date_ref = datetime.now().strftime('%Y-%m-%d')
    if date_ref.month in (1,3,5,7,8,10,12):
        date_ref.day = 31
    elif date_ref.month in (4,6,9,11):
        date_ref.day = 30
    elif date_ref.month == 2:
        if date_ref.year % 400 == 0:
            date_ref.day = 29
        else :
            date_ref.day = 28
    date_ref = str(date_ref.year) + '-' + str(date_ref.month) + '-' + str(date_ref.day)
    pt = self.browse(cr, uid, id, context=context)
    amount = value
    result = []
    obj_precision = self.pool.get('decimal.precision')
    prec = obj_precision.precision_get(cr, uid, 'Account')
    for line in pt.line_ids:
        if line.value == 'fixed':
            amt = round(line.value_amount, prec)
        elif line.value == 'procent':
            amt = round(value * line.value_amount, prec)
        elif line.value == 'balance':
            amt = round(amount, prec)
        if amt:
            next_date = (datetime.strptime(date_ref, '%Y-%m-%d') + relativedelta(days=line.days))
            if line.days2 < 0:
                next_first_date = next_date + relativedelta(day=1) #Getting 1st of required month
                next_date = next_first_date + relativedelta(days=line.days2)
            if line.days2 > 0:
                next_date += relativedelta(day=line.days2)
            result.append( (next_date.strftime('%Y-%m-%d'), amt) )
            amount -= amt

    amount = reduce(lambda x,y: x+y[1], result, 0.0)
    dist = round(value-amount, prec)
    if dist:
        result.append( (time.strftime('%Y-%m-%d'), dist) )
    return result
#class account_payment_term_line(osv.osv):
#    _inherit = 'account.payment.term.line'
#    _name = 'account.payment.term.line'
#   _columns = {
#       'months': fields.integer('Months', required=True, help="Month, set 0 for the last day of the current month. This adds complete months to the calculation."),
#   }
#    _defaults = {
#        'months': 0,
#   }
#account_payment_term_line()

my monthly_payment_term_view.xml :

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
    <data>

        <record id="monthly_payment_term_view" model="ir.ui.view">
            <field name="name">account.view_payment_term_line_form</field>
            <field name="inherit_id" ref="account.view_payment_term_line_form"/>
            <field name="model">account.payment.term.line</field>
            <field name="arch" type="xml">
                <xpath expr="//field[@name='days']" position="before">
                    <field name="months"/>
                </xpath>
            </field>
        </record>

    </data>
</openerp>

Thanks