This method will write the form name on state change from draft to confirm:

production_type = fields.Selection([
    ('budgeted','Budgeted'),
    ('nonbudgeted','Non Budgeted'),
    ('direct','Direct Order'),
], string='Type of Order', index=True, copy=False,
help=" ")
state = fields.Selection([
        ('draft','Draft'),
        ('confirm','Confirmed'),
        ('inprogress','In progress'),
        ('print_order_inprogress','Print In Progress'),
        ('finished','Finished'),
        ('cancel','Cancel'),
    ], string='State', index=True, copy=False,
    help=" ")

@api.one
def prod_start_func(self):
    name = '/'
    if self.production_type == 'budgeted':
            name = self.env['ir.sequence'].next_by_code('bsi.production.budgeted') or '/'
    elif self.production_type == 'nonbudgeted':
            name = self.env['ir.sequence'].next_by_code('bsi.production.non_budgeted') or '/'
    elif self.production_type == 'direct':
            name = self.env['ir.sequence'].next_by_code('bsi.production.direct') or '/'

    self.write({
            'state': 'confirm',
            'name' : lambda self, cr, uid, context: self.pool.get('ir.sequence').next_by_code(cr, uid, 'bsi.production.order') or '',
            })

But everytime I try to save it, it throws me this:

Traceback (most recent call last):
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\.\openerp\http.py", line 546, in _handle_exception
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\.\openerp\http.py", line 583, in dispatch
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\.\openerp\http.py", line 319, in _call_function
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\.\openerp\service\model.py", line 118, in wrapper
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\.\openerp\http.py", line 316, in checked_call
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\.\openerp\http.py", line 812, in __call__
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\.\openerp\http.py", line 412, in response_wrap
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\openerp\addons\web\controllers\main.py", line 944, in call_kw
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\openerp\addons\web\controllers\main.py", line 936, in _call_kw
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\.\openerp\api.py", line 268, in wrapper
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\.\openerp\api.py", line 373, in old_api
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\.\openerp\api.py", line 291, in <lambda>
File "C:\Program Files (x86)\Odoo 8.0-20170914\server\.\openerp\models.py", line 4057, in <lambda>
AttributeError: 'NoneType' object has no attribute 'id'

I think it has something to do with this line 'name' : lambda self, cr, uid, context: self.pool.get('ir.sequence').next_by_code(cr, uid, 'bsi.production.order') or '', but if I change it to 'name': name, I got the same result.

Any ideas?