Bluebrint causes 404 not found

[tbensonwest]

I ran the code from the command line in the final folder of ch06_routing using flask run but get 404 not found for both the homepage and the about page. This was the same when I followed along. The app worked fine before I added the blueprint.

I have a windows 10 machine with python 3.7.3 and I'm using a virtual environment.

[mikeckennedy]

Hi. This often happens when running the app doesn't necessarily register the blue print. How are you running it? python app.py or flask run-style? Make sure that the register blueprint calls are actually being called. :)

[tbensonwest]

Hey Mike

So I've kinda figured out the cause, but unsure of how to resolve entirely.

It seems that when calling flask run from the command line in a venv the executable skips over main entirely.

if __name__ == '__main__':
main()

__name__ == 'app' so main() is not called and therefore the blueprints aren't registered.

Here's the full app.py:

import sys
import flask

app = flask.Flask(__name__)

def main():
    register_blueprints()
    app.run(debug=True)

def register_blueprints():
    from views import home_views
    app.register_blueprint(home_views.blueprint)

if __name__ == '__main__':
    main()

If I remove the conditional and call main() the app works as expected but I get a warning:

c:\temp\work\pypi_org\app.py:9: Warning: Silently ignoring app.run() because the application is run from the flask command line executable. Consider putting app.run() behind an if name == "main" guard to silence this warning.
app.run(debug=True)

Do you know what may be the issue?

[mikeckennedy]

Hi. Yes, that's the problem. You're setting up the blueprints in main() but flask run doesn't execute main(). It just imports app, then calls app.run() itself (not a fan really). But if you want this to work both ways, change it to:

import sys
import flask

app = flask.Flask(__name__)

def main():
    app.run(debug=True)

def register_blueprints():
    from views import home_views
    app.register_blueprint(home_views.blueprint)

register_blueprints()
if __name__ == '__main__':
    main()

That'll do what you want and keep flask run working.