Running Flask with Gunicorn raises TypeError: index() takes 0 positional arguments but 2 were given

Question

I'm trying to run a Flask app with Gunicorn. When I run gunicorn app:index, I get the error TypeError: index() takes 0 positional arguments but 2 were given. None of the examples I've seen show index needing two parameters. What does this error mean? How do I run Flask with Gunicorn?

from flask import Flask

app = Flask(__name__)

@app.route("/")
def index():
    return 'Hello, World!'

gunicorn app:index

    respiter = self.wsgi(environ, resp.start_response)
TypeError: index() takes 0 positional arguments but 2 were given

I changed index to take two arguments, but got a different error.

@app.route("/")
def index(arg1, arg2):
    return 'Hello, World!'

  /python3.4/site-packages/flask/templating.py, line 132, in render_template
    ctx.app.update_template_context(context)
AttributeError: 'NoneType' object has no attribute 'app'

Answer 1

You have to pass a Flask instance to gunicorn, not a function name like you did with index. So if your app saved as app.py, then you have to run gunicorn as follows:

$ gunicorn --bind 127.0.0.1:8000 app:app