Flask-Babel language selector

Question

Hello it is a pleasure to greet you, today I come to ask you for help with an error that Babel de Flask is presenting to me, I am new to the subject, but in advance I thank you for your collaboration.

At the end of the code I show in a Quote the error message.

Next the code used.

My adds init.py

import os
from flask import Flask, request
from werkzeug.datastructures import ImmutableDict
import flask_babel as babel
from flask_babel import gettext as _

b = babel.Babel()
app = Flask(__name__, instance_relative_config=True)
b.init_app(app)

@babel.localeselector
    def get_locale():
        # if the user has set up the language manually it will be stored in the session,
        # so we use the locale from the user settings
        try:
            language = session['language']
        except KeyError:
            language = None
        if language is not None:
            return language
        return request.accept_languages.best_match(passbyte.config['LANGUAGES'].keys())

@app.route('/language/<language>')
def set_language(language=None):
    session['language'] = language
    return redirect(url_for('home'))
            
@app.context_processor
def inject_conf_var():
    return dict(AVAILABLE_LANGUAGES=app.config['LANGUAGES'], CURRENT_LANGUAGE=session.get('language',request.accept_languages.best_match(app.config['LANGUAGES'].keys())))

My > config.py

# -*- coding: utf-8 -*-
# ...
# available languages
LANGUAGES = {
    'en': 'English',
    'es': 'Español'
}

My base.html

            {% for language in AVAILABLE_LANGUAGES.items() %}
            {% if CURRENT_LANGUAGE == language[0] or (CURRENT_LANGUAGE == '' and BEST_MATCH_LANGUAGE == language[0]) %}
              <li class="lang_active"><a name="language">{{ language[1] }}</a></li>
            {% else %}
              <li class="lang_inactive"><a href="?lang={{ language[0] }}">{{ language[1] }}</a></li>
            {%  endif %}
            {% endfor %}

The error

jinja2.exceptions.UndefinedError: 'AVAILABLE_LANGUAGES' is undefined

I see my code here

score 2 · Answer 1 · answered Aug 07 '20 at 20:56

@babel.localselector should be @b.localselector.

Explanation: You created an app object from Flask(), the decorators use the app object not Flask directly, then you should do the same with babel. You created a b (babel object), so use it.

It seems also that you do not load the configuration. Then, the app.config[*] probably returns None. So you need to load it somewhere:

app = Flask(__name__, instance_relative_config=True)
app.config.from_object('yourapplication.default_settings')
# or
app.config.from_pyfile('application.cfg', silent=True)

Look the official documentation for more details depending on your case: Configuration Handling

Flask-Babel language selector

1 Answers1