partner-contact/partner_contact_gender/models/res_partner.py

# Copyright 2014-2015 Grupo ESOC <www.grupoesoc.es>
# Copyright 2017-Apertoso N.V. (<http://www.apertoso.be>)
# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).

from odoo import fields, models


class ResPartner(models.Model):
    _inherit = 'res.partner'

    gender = fields.Selection([
        ('male', 'Male'),
        ('female', 'Female'),
        ('other', 'Other')
    ])