Flask-Language is a Flask extension providing a simple mechanism to handle a client-side language cookie.

It is somewhat loosely based on this snippet: http://flask.pocoo.org/snippets/128

Install the extension with with pipenv (recommended):

$ pipenv install flask-language

Or with pip:

$ pip install flask-language

Initialize the Flask-Language extension (also compatible with the Application Factories pattern):

from flask import Flask, jsonify
from flask_language import Language, current_language

app = Flask(__name__)
lang = Language(app)

Define the language hooks:

@lang.allowed_languages
def get_allowed_languages():
    return ['en', 'fr']

@lang.default_language
def get_default_language():
    return 'en'

Define the desired end-points to retrieve and manipulate the current language:

@app.route('/api/language')
def get_language():
    return jsonify({
        'language': str(current_language),
    })

@app.route('/api/language', methods=['POST'])
def set_language():
    req = request.get_json()
    language = req.get('language', None)

    lang.change_language(language)

    return jsonify({
        'language': str(current_language),
    })

Before each request, Flask-Language will automatically determine the current language in the following order:

1. The language cookie (if any and matching the allowed languages)
2. The Accept-Language HTTP header (if any and matching the allowed languages)
3. The provided default language

During each request context, the current language can be accessed using current_language.

After each request, the current language will be stored in the language cookie.

Flask-Language is configurable via the following configuration variables:

• LANGUAGE_COOKIE_NAME: name for the cookie language (default: 'lang')
• LANGUAGE_COOKIE_TIMEOUT: validity duration of the cookie language (default: datetime.timedelta(days=365))
• LANGUAGE_COOKIE_DOMAIN: domain for the cookie language (default: None)
• LANGUAGE_COOKIE_SECURE: set secure option for the cookie language (default: False)
• LANGUAGE_COOKIE_HTTPONLY: set HTTP-only for the cookie language (default: False)

The Sphinx-compiled documentation is available on ReadTheDocs.

The MIT License (MIT)

Copyright (c) 2018 Romain Clement