Multi-Page Dash App Plugin

A plugin to simplify creating multi-page Dash apps. This is a preview of functionality that will of Dash 2.1.

Background

The goal of this plugin is to remove as much boilerplate as possible when creating multi-page Dash apps.

This plugin allows users to simply place their layouts in pages/ and call dash.register_page with the desired URL path of that page.

This plugin will automatically:

Create the URL routing callback
Add page information to dash.page_registry that can be used when creating navigation bars
Set validate_layout accordingly so that you don’t need to suppress_callback_exceptions for simple multi-page layouts
Set the order of dash.page_registry based off order and the filename
Set <title> and <meta description> and their social media equivalents accordingly in the index_string of the HTML that is served on page-load
Set a clientside callback to update the <title> as you navigate pages with dcc.Link
Set the social media meta image accordingly based off of images available in assets

Usage

Option 1 – In this project

Clone this repo and then run python app.py. pages_plugin.py is the functionality that will become part of the dash library. The pages/ folder demonstrates examples of how to use dash.register_page.

Option 2 – In your own projects

Copy pages_plugin.py into your project folder. In the future, this will be part of dash and you won’t need to copy this file.
In app.py, pass the plugin into Dash:

import pages_plugin

app = Dash(__name__, plugins=[pages_plugin])

Create a folder called pages/ and place your app layouts in files within that folder. Each file needs to:

Define layout. This can be a variable or function that returns a component
Call dash.register_page(__name__) to tell pages_plugin that this page should be part of the multi-page framework

For example:
pages/historical_outlook.py

import dash
from dash import html

dash.register_page(__name__)

def layout():
    return html.Div('This page is the historical outlook')

dash.register_page will can accept various arguments to customize aspects about the page like path (the URL of the page), title (the browser tab’s title of the page), and more. See the API reference below for details.

pages/home.py

import dash
from dash import html

dash.register_page(
    __name__,
    path='/',
    title='Analytics App'
)

def layout():
    return html.Div('This is the home page')

Modify app.layout to display the URLs for page navigation and include the container that displays the page’s content.

dash.page_registry: The page URLs can be found in dash.page_registry. This is an OrderedDict with keys being the page’s module name (e.g. pages.historical_outlook) and values being a dictionary containing keys path, name, order, title, description, image, and layout. This page_registry is populated from calling dash.register_page within pages/.
pages_plugin.page_container: This component defines where the page’s content will render on page navigation.

app.py

import pages_plugin

app = Dash(__name__, plugins=[pages_plugin])

app.layout = html.Div([
    # Display the URLs by looping through `dash.page_registry`
    # In practice, this might be a `ddk.Header` or a `dbc.NavbarSimple`
    html.Div([dcc.Link(page['name'], href=page['path']) for page in dash.page_registry),
    
    html.Hr()
    
    # Set the container where the page content will be rendered into on page navigation
    pages_plugin.page_container
])

Refrence

dash.register_page

def register_page(
    module,
    path=None,
    name=None,
    order=None,
    title=None,
    description=None,
    image=None,
    layout=None,
    **kwargs
):

Assigns the variables to dash.page_registry as an OrderedDict
(ordered by order).

dash.page_registry is used by pages_plugin to set up the layouts as
a multi-page Dash app. This includes the URL routing callbacks
(using dcc.Location) and the HTML templates to include title,
meta description, and the meta description image.

dash.page_registry can also be used by Dash developers to create the
page navigation links or by template authors.

module:
The module path where this page’s layout is defined. Often __name__.
path:
URL Path, e.g. / or /home-page.
If not supplied, will be inferred from module,
e.g. pages.weekly_analytics to /weekly-analytics
name:
The name of the link.
If not supplied, will be inferred from module,
e.g. pages.weekly_analytics to Weekly analytics
order:
The order of the pages in page_registry.
If not supplied, then the filename is used and the page with path / has
order 0
title:
The name of the page <title>. That is, what appears in the browser title.
If not supplied, will use the supplied name or will be inferred by module,
e.g. pages.weekly_analytics to Weekly analytics
description:
The .
If not supplied, then nothing is supplied.
image:
The meta description image used by social media platforms.
If not supplied, then it looks for the following images in assets/:
- A page specific image: assets/<title>.<extension> is used, e.g. assets/weekly_analytics.png
- A generic app image at assets/app.<extension>
- A logo at assets/logo.<extension>
layout:
The layout function or component for this page.
If not supplied, then looks for layout from within the supplied module.
**kwargs:
Arbitrary keyword arguments that can be stored

page_registry stores the original property that was passed in under
supplied_<property> and the coerced property under <property>.
For example, if this was called:

register_page(
    'pages.historical_outlook',
    name='Our historical view',
    custom_key='custom value'
)

Then this will appear in page_registry:

OrderedDict([
    (
        'pages.historical_outlook', 
        dict(
            module='pages.historical_outlook',
            
            supplied_path=None,
            path='/historical-outlook',
            
            supplied_name='Our historical view',
            name='Our historical view',
            
            supplied_title=None,
            title='Our historical view'
            
            supplied_description=None,
            description='Our historical view',
            
            supplied_order=None,
            order=1,
            
            supplied_layout=None,
            layout=<function pages.historical_outlook.layout>,
            
            custom_key='custom value'
        )
    ),
])