Implement internationalization (i18n) and localization (l10n) support in your Flask application by adding your own translations, language support, and allow users to swap between languages using the language option switcher.
These instructions will get you a copy of the project up and running on your local machine.
- Git clone or download the project files.
git clone https://github.com/hazzillrodriguez/flask-multi-language.git
cd flask-multi-language
- Create and activate the virtual environment then install requirements.
python -m venv env
source env/Scripts/activate
pip install -r requirements.txt
- Start the development web server.
export FLASK_APP=run
export FLASK_ENV=development
flask run
Open config.py and add your own supported languages.
class BaseConfig(object):
# Here you can list all the languages that you want to use in your application
LANGUAGES = {
'en': 'English',
'zh': 'Chinese',
'de': 'German'
}If you need to be more specific, a country code can be added as well. For example, you could use en-US, en-GB, and en-CA to support American, British, and Canadian English as different languages.
The way you will communicate to Babel that you want something translated in your templates will be by using the following format (parentheses preceded by an underscore).
<h1>{{ _('Hello world!') }}</h1>
<div>{{ form.email(placeholder=_('user@example.com')) }}</div>
<input type="email" id="email" name="email" placeholder={{ _('E-mail address') }}>
Additionally, if you want to use constant strings somewhere in your application and define them outside of a request, you can use a lazy string. Lazy strings will not be evaluated until they are actually used. To use such a lazy string, use the lazy_gettext() function.
from flask_babel import lazy_gettext
class EmailForm(FlaskForm):
email = StringField(lazy_gettext('E-mail address'))Flask uses gettext together with Babel. The idea of gettext is that you can mark certain strings as translatable and a tool will pick all those up, collect them in a separate file for you to translate.
from flask_babel import gettext
flash(gettext('Your email or password is incorrect!'))After marking all the texts in your templates and python source code, you can now generate a new language catalog in the translations directory for the language you specified in the <language-code> option. To add a new language, use the command.
flask translate init <language-code>
This command will create a subdirectory of the new supported language inside the translations directory. There will be a new file named messages.po, which is where the translations need to be made.
Below you can see an example of the German messages.po after I added the translations.
#: app/templates/index.html:9
msgid "Hello world!"
msgstr "Hallo Welt!"
#: app/templates/index.html:10
msgid "Lets all be unique together until we realise we are all the same."
msgstr "Lasst uns alle gemeinsam einzigartig sein, bis wir erkennen, dass wir alle gleich sind."
#: app/templates/index.html:11
msgid "Two more days and all his problems would be solved."
msgstr "Noch zwei Tage und alle seine Probleme wären gelöst."
The msgid line contains the text in the base language, and the msgstr line that follows contains an empty string. Those empty strings need to be edited to have the version of the text in the target language.
To compile all the translations for the application, you can use the flask translate compile command as follows.
flask translate compile
To update all the languages after making changes to the _(), gettext(), and lazy_gettext() language markers.
flask translate update
After the messages.po are updated, you can go ahead and compile the messages one more time to make them available to the application.
flask translate compile
Distributed under the MIT License. See LICENSE for more information.
Hazzill Rodriguez — LinkedIn — hazzillrodriguez@gmail.com