Do you mean this Flask_Redis: https://pypi.python.org/pypi/Flask-Redis/0.0.5 ?
If so, there is a better way to handle this than placing it in the URL. According to the docs, in your Flask config place the following:
REDIS_HOST = "localhost"
REDIS_PASSWORD = "password"
REDIS_PORT = 6379
If placing the config in code, as in your example:
app.config["REDIS_PASSWORD"] = 'password'
Doing this in the config should be more maintainable and configurable without modifying code.