Description of my usage: This is my project structure(basically base on Flask Web Development): Configuration in /babel.cfg and /app/__init__.py babel.cfg: app/__init__.py: Then I follow the Flask-Babel document Run $ pybabel extract -F babel.cfg -o messages.pot . Run $ pybabel extract -F babel.cfg -k lazy_gettext -o messages.pot . They do have found all the gettexts and lazy_gettexts. Run $ pybabel init