How to change language of flask babel on a button click?

Question

I have the function in Flask, which returns the website in english. Moreover, i want to be able to use german in the website at a button push from html. How can I change the language at a button push from english to german and from german to english? Also, is it possible to use the function get_locale only at call, not running automatically?

@babel.localeselector
def get_locale():
     return 'en'  

Answer 1

At first You need to store the address at the main app file:

@app.route('/language=<language>')
def set_language(language=None):
    session['language'] = language
    return redirect(url_for('home'))

Than You need to change to the same addess to get_locale function in main app file:

@babel.localeselector
def get_locale():
    if request.args.get('language'):
        session['language'] = request.args.get('language')
    return session.get('language', 'en')

To access current language from template:

app.config['LANGUAGES'] =  {
    'en': 'English',
    'ge': 'German',
}
app.secret_key = "super secret key"

    @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())))

Here the template file:

{% for language in AVAILABLE_LANGUAGES.items() %}
    {% if CURRENT_LANGUAGE == language[0] %}
        {{ language[1] }}
    {% else %}
        <a href="{{ url_for('set_language', language=language[0]) }}" >{{ language[1] }}</a>
    {%  endif %}
{% endfor %}