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How to Embed D-Tale Within a Django App

Install Dependencies & Create Django Sample App

To start off run the following commands within your virtual environment:

home:~ pip install dtale
home:~ pip install Django
home:~ django-admin startproject dtale_test

Add dispatcher.py

The Django project should have created the following folder: dtale_test/dtale_test

Navigate to that folder and add create a file dispatcher.py containing the following code:

from threading import Lock
from werkzeug.wsgi import pop_path_info, peek_path_info

class PathDispatcher(object):

    def __init__(self, default_app, create_app):
        self.default_app = default_app
        self.create_app = create_app
        self.lock = Lock()
        self.instances = {}

    def get_application(self, prefix):
        with self.lock:
            app = self.instances.get(prefix)
            if app is None:
                app = self.create_app(prefix)
                if app is not None:
                    self.instances[prefix] = app
            return app

    def __call__(self, environ, start_response):
        app = self.get_application(peek_path_info(environ))
        if app is not None:
            pop_path_info(environ)
        else:
            app = self.default_app
        return app(environ, start_response)

This will allow wsgi to route between your Django application and D-Tale's Flask application.

Adding Your Views

Go go dtale_test/dtale_test/views.py and update it to contain the following:

import pandas as pd

from django.http import HttpResponse
from django.shortcuts import redirect

from dtale.views import startup


def index(request):
    return HttpResponse("""
        <h1>Django/Flask Hybrid</h1>
        <span>Generate sample dataframe in D-Tale by clicking this </span><a href="/create-df">link</a>
    """)


def create_df(request):
    df = pd.DataFrame(dict(a=[1, 2, 3], b=[4, 5, 6]))
    instance = startup(data=df, ignore_duplicate=True)

    resp = redirect(f"/flask/dtale/main/{instance._data_id}")
    return resp
  • create_df: by hitting this view you will create a simple pandas dataframe and store it in D-Tale.
    • Using the dtale.views.startup function will store your dataframe in D-Tale and assign it an auto-generated id, '1'
    • Once startup completes this dataframe should be available to be viewed from the D-Tale Flask process at the route, /dtale/main/1
    • We'll jump to it by using redirect. Please take a second to note the prefix /flask on our route to D-Tale, that will come into play later.
  • index: just a simple main view which includes some HTML with a link to the create-df route which we'll map later to our create_df view function

Mapping views to routes

Navigate to dtale_test/dtale_test/urls.py and add the following:

from django.contrib import admin
from django.urls import path

from . import views

urlpatterns = [
    path('', views.index, name='index'),
    path('create-df/', views.create_df, name='create-df'),
    path('admin/', admin.site.urls),
]

This code will map our Django views to routes available from your browser. We will leave the route to the index view as an empty string so that way when you hit the host & port of your Django app it will default to that view.

Update wsgi.py To Use the Dispatcher

Navigate to dtale_test/dtale_test/wsgi.py and add the following code:

import os

from django.core.wsgi import get_wsgi_application
from dtale.app import build_app

from .dispatcher import PathDispatcher

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'dtale_test.settings')


def make_app(prefix):
    if prefix == 'flask':
        return build_app(app_root='/flask', reaper_on=False)


application = PathDispatcher(get_wsgi_application(), make_app)

What this code will do is use the PathDispatcher class we created earlier to check any incoming requests to see if their route starts with the prefix /flask and if it does re-route them to D-Tale using it's build_app function. Anything else will be routed to the Django views we created (create_df & index)

Couple Things To Take Note Of

  • build_app will only be called once because each prefix that comes into PathDispatcher will be store app associated to it in a dictionary so that we won't continually creating Flask apps.
  • Any routes you've seen D-Tale previously will now, for the purposes of this application, will be prefixed with /flask. The app_root parameter to the build_app function will handle this for us. Also, you can name set your prefix to whatever you'd like it doesn't have to be /flask.

Putting It All Together

It's now time to run this thing. :)

  • Go to your command-line and navigate to the first dtale_test folder containing the manage.py file and run the following command:
python manage.py runserver
  • Once you see this output: Starting development server at http://127.0.0.1:8000/
  • Go to any browser and hit the url: http://127.0.0.1:8000
  • This should bring you to the output of the index view function we defined earlier.
  • Click the link and it will fire the contents of the create_df function and then re-route you to D-Tale
  • Look at the location in your browser and you'll see that it's pointing at /flask/dtale/main/1
  • It's using the /flask prefix as we expected!

You're now running a Django application & a Flask application together. The world is your oyster!

Hope this helps and support open-source by putting your ⭐ on this repo!