python - Running a Dash app within a Flask app

Question

I have an existing Flask app, and I want to have a route to another app. More concretely, the second app is a Plotly Dash app. How can I run my Dash app within my existing Flask app?

@app.route('/plotly_dashboard') 
def render_dashboard():
    # go to dash app

I also tried adding a route to the Dash instance, since it's a Flask app, but I get the error:

AttributeError: 'Dash' object has no attribute 'route'

Answer 1

From the docs:

The underlying Flask app is available at app.server.

import dash
app = dash.Dash(__name__)
server = app.server

You can also pass your own Flask app instance into Dash:

import flask
server = flask.Flask(__name__)
app = dash.Dash(__name__, server=server)

Now that you have the Flask instance, you can add whatever routes and other functionality you need.

@server.route('/hello')
def hello():
    return 'Hello, World!'

---

To the more general question "how can I serve two Flask instances next to each other", assuming you don't end up using one instance as in the above Dash answer, you would use DispatcherMiddleware to mount both applications.

dash_app = Dash(__name__)
flask_app = Flask(__name__)

application = DispatcherMiddleware(flask_app, {'/dash': dash_app.server})