partner-contact/base_location/models/res_city.py

# Copyright 2018 Aitor Bouzas <aitor.bouzas@adaptivecity.com>
# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).

from odoo import fields, models


class City(models.Model):
    _inherit = 'res.city'

    zip_ids = fields.One2many('res.city.zip', 'city_id',
                              string="Zips in this city")

    _sql_constraints = [
        ('name_state_country_uniq',
         'UNIQUE(name, state_id, country_id)',
         'You already have a city with that name in the same state.'
         'The city must have a unique name within '
         'it\'s state and it\'s country'),
    ]