Making Your Odoo Modules Translation-Ready: i18n Best Practices

from odoo import models, fields, _

class SaleOrder(models.Model):
    _name = 'sale.order'
    _description = _('Sale Order')  # Translatable description
    
    # Field labels with translations
    customer_id = fields.Many2one(
        'res.partner',
        string=_('Customer'),  # Mark as translatable
        help=_('Select the customer for this order')
    )
    
    status = fields.Selection(
        selection=[
            ('draft', _('Draft')),
            ('sent', _('Quotation Sent')),
            ('sale', _('Order Confirmed')),
            ('done', _('Done')),
            ('cancel', _('Cancelled')),
        ],
        string=_('Status'),
        default='draft'
    )
    
    # Error messages (translatable)
    def action_confirm(self):
        if not self.customer_id:
            raise ValidationError(_('Customer is required to confirm order'))
        self.state = 'sale'

<record id="view_order_form" model="ir.ui.view">
    <field name="name">Sale Order</field>
    <field name="model">sale.order</field>
    <field name="arch" type="xml">
        <form>
            <sheet>
                <!-- Field labels auto-translatable in views -->
                <field name="customer_id"/>
                
                <!-- String attribute (translatable) -->
                <separator string="Order Details"/>
                
                <!-- Button labels (translatable) -->
                <button name="action_confirm" type="object" 
                        string="Confirm Order" class="btn-primary"/>
            </sheet>
        </form>
    </field>
</record>

# ❌ WRONG - Not translatable
def action_confirm(self):
    raise ValidationError('Customer is required')  # Hard-coded, won't translate

# ✅ RIGHT - Translatable
def action_confirm(self):
    raise ValidationError(_('Customer is required'))

custom_module/
├── models/
├── views/
├── i18n/                      # Translation folder
│   ├── custom_module.pot      # Translation template (source strings)
│   ├── fr_FR.po               # French translations
│   ├── es_ES.po               # Spanish translations
│   ├── de_DE.po               # German translations
│   └── ar_AR.po               # Arabic translations
└── __manifest__.py

# Translation file for custom_module

#. Field string in model sale.order
#: model:ir.model.fields,string:custom_module.field_sale_order__customer_id
msgid "Customer"
msgstr "Client"

#. Selection value
#: model:ir.model.fields.selection,string:custom_module.selection_sale_order__state__draft
msgid "Draft"
msgstr "Brouillon"

#. Button label
#: model:ir.actions.act_window,name:custom_module.action_sale_order
msgid "Sale Orders"
msgstr "Commandes de Vente"

#. Error message
#: code:addons/custom_module/models/sale_order.py:0
msgid "Customer is required to confirm order"
msgstr "Le client est obligatoire pour confirmer la commande"

msgid "Customer"
msgstr "Cliente"  # Spanish

msgid "Sale Orders"
msgstr "Pedidos de Venta"  # Spanish

custom_module/i18n/es_ES.po  # Spanish
custom_module/i18n/fr_FR.po  # French
custom_module/i18n/de_DE.po  # German

class Product(models.Model):
    _inherit = 'product.product'
    
    # Regular field (not translatable)
    name = fields.Char(string='Name')
    
    # Translatable field (changes per language)
    description = fields.Text(
        string='Description',
        translate=True,  # KEY: Enables per-language content
        help='Product description (translates to each language)'
    )
    
    care_instructions = fields.Text(
        string='Care Instructions',
        translate=True  # Each language has different instructions
    )

from odoo import models, fields, api, _

class ProductTemplate(models.Model):
    _inherit = 'product.template'
    
    # Translatable fields
    name = fields.Char(
        string=_('Product Name'),
        translate=True,  # Translates to each language
        required=True
    )
    
    description = fields.Html(
        string=_('Description'),
        translate=True
    )
    
    care_instructions = fields.Text(
        string=_('Care Instructions'),
        translate=True,
        help=_('How to care for this product')
    )
    
    size_guide = fields.Html(
        string=_('Size Guide'),
        translate=True,
        help=_('Translatable size guide HTML')
    )
    
    # Regular fields (NOT translated)
    sku = fields.Char(string=_('SKU'))
    barcode = fields.Char(string=_('Barcode'))
    list_price = fields.Float(string=_('List Price'))
    
    @api.constrains('name')
    def _check_name(self):
        for product in self:
            if not product.name:
                raise ValidationError(_('Product name is required'))

<record id="view_product_form" model="ir.ui.view">
    <field name="name">Product Form</field>
    <field name="model">product.template</field>
    <field name="arch" type="xml">
        <form>
            <sheet>
                <!-- Translatable field -->
                <field name="name"/>
                
                <!-- Regular field (not translated) -->
                <field name="sku"/>
                
                <!-- Translatable HTML field -->
                <field name="description" widget="html"/>
                
                <!-- Translatable multi-line field -->
                <field name="care_instructions"/>
            </sheet>
        </form>
    </field>
</record>

# Activate French
lang = self.env['res.lang'].search([('code', '=', 'fr_FR')])
if lang:
    lang.active = True

# Add language if doesn't exist
self.env['res.lang'].create({
    'name': 'French',
    'code': 'fr_FR',
    'iso_code': 'fr',
    'active': True,
})

# Set user to use French
user = self.env.user
user.lang = 'fr_FR'

# Now when user accesses system, everything is in French

# Get customer's language
customer = self.env['res.partner'].browse(customer_id)
customer_lang = customer.lang

# Fetch product in customer's language
product = self.env['product.product'].with_context(lang=customer_lang).browse(product_id)

# Now product.description is in customer's language

# ✅ DO THIS
from odoo import _, models

class MyModel(models.Model):
    name = fields.Char(string=_('Name'))
    
    def action(self):
        raise ValidationError(_('Error message'))

# ❌ DON'T DO THIS
class MyModel(models.Model):
    name = fields.Char(string='Name')  # No _()
    
    def action(self):
        raise ValidationError('Error message')  # Hard-coded

# ✅ DO THIS
description = fields.Text(
    string=_('Description'),
    translate=True,
    help=_('Product description'))

# ❌ DON'T DO THIS
description = fields.Text(string='Description')  # No translate=True