Flask and uWSGI – unable to load app 0 (mountpoint=”) (callable not found or import error)

I get the below error when I try and start Flask using uWSGI.
Here is how I start:

>  # cd ..
>     <a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="74061b1b0034181b1715181c1b0700">[email protected]</a>:# uwsgi --socket 127.0.0.1:6000 --file /path/to/folder/run.py --callable app -  -processes 2

Here is my directory structure:

-/path/to/folder/run.py
      -|app
          -|__init__.py
          -|views.py
          -|templates
          -|static

Contents of /path/to/folder/run.py

if __name__ == '__main__':
   from app import app
   #app.run(debug = True)
   app.run()

Contents of /path/to/folder/app/__init__.py

import os
from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy
from flask.ext.login import LoginManager
#from flaskext.babel import Babel
from config import basedir
app = Flask(__name__)
app.config.from_object('config')
#app.config.from_pyfile('babel.cfg')

db = SQLAlchemy(app)
login_manager = LoginManager()
login_manager.setup_app(app)
login_manager.login_view = 'login'
login_manager.login_message = u"Please log in to access this page."

from app import views

*** Operational MODE: preforking ***
unable to find "application" callable in file /path/to/folder/run.py
unable to load app 0 (mountpoint='') (callable not found or import error)
*** no app loaded. going in full dynamic mode ***
*** uWSGI is running in multiple interpreter mode ***
spawned uWSGI worker 1 (pid: 26972, cores: 1)
spawned uWSGI worker 2 (pid: 26973, cores: 1)

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

I had problems with the accepted solution because my flask app was in a variable called app. You can solve that with putting just this in your wsgi:

from module_with_your_flask_app import app as application

So the problem was simply that uwsgi expects a variable called application.

Method 2

uWSGI doesn’t load your app as __main__, so it never will find the app (since that only gets loaded when the app is run as name __main__). Thus, you need to import it outside of the if __name__ == "__main__": block.

Really simple change:

from app import app as application  # for example, should be app

if __name__ == "__main__":
    application.run()

Now you can run the app directly with python run.py or run it through uWSGI the way you have it.

NOTE: if you set --callable myapp, you’d need to change it from as application to myapp (by default uwsgi expects application

Method 3

The uWSGI error unable to load app 0 (mountpoint='') (callable not found or import error) occured for me if I left out the last two lines of the following minimal working example for Flask application

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello world!"

if __name__ == "__main__":
    app.run()
else:
    application = app

I am aware that this already implicitly said within the comments to another answer, but it still took me a while to figure that out, so I hope to save others’ time.

In the case of a pure Python Dash application, I can offer the following minimal viable code snippet:

import dash
import dash_core_components as dcc
import dash_html_components as html
app = dash.Dash()
app.layout = html.Div( html.H1(children="Hello World") )

application = app.server

if __name__ == "__main__":
    app.run_server(debug=True)

Again, the application = app.server is the essential part here.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0