bokeh-django

Support for running Bokeh apps with Django

Introduction

Both Bokeh and Django are web frameworks that can be used independently to build and host web applications. They each have their own strengths and the purpose of the bokeh_django package is to integrate these two frameworks so their strengths can be used together.

Installation

pip install bokeh-django

Configuration

This documentation assumes that you have already started a Django project.

bokeh-django enables you to define routes (URLs) in your Django project that will map to Bokeh applications or embed Bokeh applications into a template rendered by Django. However, before defining the routes there are several configuration steps that need to be completed first.

Configure INSTALLED_APPS:

In the settings.py file ensure that both channels and bokeh_django are added to the INSTALLED_APPS list:
```
INSTALLED_APPS = [
    ...,
    'channels',
    'bokeh_django',
]
```

Set Up an ASGI Application:

By default, the Django project will be configured to use a WSGI application, but the startproject command should have also created an asgi.py file.

In settings.py change the WSGI_APPLICATION setting to ASGI_APPLICATION and modify the path accordingly. It should look something like this:

ASGI_APPLICATION = 'mysite.asgi.application'

Next, modify the contents of the asgi.py file to get the URL patterns from the bokeh_django app config. Something similar to this will work:

from channels.auth import AuthMiddlewareStack
from channels.routing import ProtocolTypeRouter, URLRouter
from django.apps import apps

bokeh_app_config = apps.get_app_config('bokeh_django')

application = ProtocolTypeRouter({
   'websocket': AuthMiddlewareStack(URLRouter(bokeh_app_config.routes.get_websocket_urlpatterns())),
   'http': AuthMiddlewareStack(URLRouter(bokeh_app_config.routes.get_http_urlpatterns())),
})

Configure Static Files:

Both Bokeh and Django have several ways of configuring serving static resources. This documentation will describe several possible configuration approaches.

The Bokeh resources setting can be set to one of several values (e.g server, inline, cdn), the default is cdn. If this setting is set to inline, or cdn then Bokeh resources will be served independently of Django resources. However, if the Bokeh resources setting is set to server, then the Bokeh resources are served up by the Django server in the same way that the Django static resources are and so Django must be configured to be able to find the Bokeh resources.

To specify the Bokeh resources setting add the following to the Django settings.py file:
```
from bokeh.settings import settings as bokeh_settings

bokeh_settings.resources = 'server'
```
If the Bokeh resources setting is set to server then we must add the location of the Bokeh resources to the STATICFILES_DIRS setting:
```
from bokeh.settings import settings as bokeh_settings

try:
    bokeh_js_dir = bokeh_settings.bokehjs_path()
except AttributeError:
    # support bokeh versions < 3.4
    bokeh_js_dir = bokeh_settings.bokehjsdir()

STATICFILES_DIRS = [
    ...,
    bokeh_js_dir,
]
```
Django can be configured to automatically find and collect static files using the staticfiles app, or the static file URL patterns can be explicitly added to the list of urlpatterns in the urls.py file.

To explicitly add the static file urlpatterns add the following to the urls.py file:
```
from django.contrib.staticfiles.urls import staticfiles_urlpatterns
from bokeh_django import static_extensions

urlpatterns = [
    ...,
    *static_extensions(),
    *staticfiles_urlpatterns(),
]
```
Be sure that the static_extensions are listed before the staticfiles_urlpatterns.

Alternatively, you can configure the staticfiles app by adding 'django.contrib.staticfiles', to INSTALLED_APPS:
```
INSTALLED_APPS = [
    ...,
    'django.contrib.staticfiles',
    'channels',
    'bokeh_django',
]
```
Next add bokeh_django.static.BokehExtensionFinder to the STATICFILES_FINDERS setting. The default value for STATICFILES_FINDERS has two items. If you override the default by adding the STATICFILES_FINDERS setting to your settings.py file, then be sure to also list the two default values in addition to the BokehExtensionFinder:
```
STATICFILES_FINDERS = (
    "django.contrib.staticfiles.finders.FileSystemFinder",
    "django.contrib.staticfiles.finders.AppDirectoriesFinder",
    'bokeh_django.static.BokehExtensionFinder',
)
```

Define Routes

Bokeh applications are integrated into Django through routing or URLs.

In a Django app, the file specified by the ROOT_URLCONF setting (e.g. urls.py) must define urlpatterns which is a sequence of django.url.path and/or django.url.re_path objects. When integrating a Django app with Bokeh, the urls.py file must also define bokeh_apps as a sequence of bokeh_django routing objects. This should be done using the bokeh_djagno.document and/or bokeh_django.autoload functions.

Document

The first way to define a route is to use bokeh_django.document, which defines a route to a Bokeh app (as either a file-path or a function).

from bokeh_django import document
from .views import my_bokeh_app_function

bokeh_apps = [
    document('url-pattern/', '/path/to/bokeh/app.py'),
    document('another-url-pattern/', my_bokeh_app_function)   
]

When using the document route Django will route the URL directly to the Bokeh app and all the rendering will be handled by Bokeh.

Autoload

To integrate more fully into a Django application routes can be created using autoload. This allows the Bokeh application to be embedded in a template that is rendered by Django. This has the advantage of being able to leverage Django capabilities in the view and the template, but is slightly more involved to set up. There are five components that all need to be configured to work together: the Bokeh handler, the Django view, the template, the Django URL path, and the Bokeh URL route.

Bokeh Handler

The handler is a function (or any callable) that accepts a bokeh.document.Document object and configures it with the Bokeh content that should be embedded. This is done by adding a Bokeh object as the document root:

from bokeh.document import Document
from bokeh.layouts import column
from bokeh.models import Slider

def bokeh_handler(doc: Document) -> None:
 slider = Slider(start=0, end=30, value=0, step=1, title="Example")
 doc.add_root(column(slider))

The handler can also embed a Panel object. In this case the document is passed in to the server_doc method of the Panel object:

import panel as pn
def panel_handler(doc: Document) -> None:
   pn.Row().server_doc(doc)

Django View

The view is a Django function that accepts a request object and returns a response. A view that embeds a Bokeh app must create a bokeh.embed.server_document and pass it in the context to the template when rendering the response.

from bokeh.embed import server_document
from django.shortcuts import render

def view_function(request):
    script = server_document(request.build_absolute_uri())
    return render(request, "embed.html", dict(script=script))

Template

The template document is a Django HTML template (e.g. "embed.html") that will be rendered by Django. It can be as complex as desired, but at the very least must render the script that was passed in from the context:

<!doctype html>
<html lang="en">  
<body>
  {{ script|safe }}
</body>
</html>

Django URL Path

The Django URL Path is a django.url.path or django.url.re_path object that is included in the urlpatters sequence and that maps a URL pattern to the Django View as would normally be done with Django.

urlpatterns = [
    path("embedded-bokeh-app/", views.view_function),
]

Bokeh URL Route

The Bokeh URL Route is a bokeh_django.autoload object that is included in the bokeh_apps sequence and that maps a URL pattern to the Bokeh handler.

from bokeh_django import autoload

bokeh_apps = [
    autoload("embedded-bokeh-app/", views.handler) 
]

Note that the URL pattern should be the same URL pattern that was used in the corresponding Django URL Path. In reality the URL pattern must match the URL that the server_document script is configured with in the Django View. Normally, it is easiest to use the URL from the request object (e.g. script = server_document(request.build_absolute_uri())), which is the URL of the corresponding Django URL Path.

bokeh / bokeh-django

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