Dashing Your Data: Creating Standalone HTML Files Like Plotly
Dash, the popular Python framework for building web applications, empowers users to create interactive dashboards and visualizations. But sometimes, you might want to share your creations outside the confines of a Dash server. This is where the ability to generate standalone HTML files, akin to Plotly's output, comes into play.
Let's dive into this process and illustrate it with a simple example:
The Problem:
You've painstakingly crafted a Dash app with captivating visualizations. Now you need to distribute this app to colleagues or embed it in another website – a standalone HTML file is the perfect solution.
The Solution:
Dash provides a method called dcc.Location that can be used to capture the current URL and generate a static HTML file. This file includes the entire application's layout, data, and interactivity, allowing it to function independently.
Code Example:
import dash
import dash_core_components as dcc
import dash_html_components as html
import plotly.express as px
app = dash.Dash(__name__)
app.layout = html.Div(children=[
html.H1(children="Hello Dash!"),
dcc.Graph(
id='interactive-graph',
figure=px.line(x=[1, 2, 3], y=[4, 5, 6])
),
dcc.Location(id='url', refresh=False), # Key component for HTML export
html.Div(id='page-content') # Placeholder for output
])
@app.callback(
dash.Output('page-content', 'children'),
[dash.Input('url', 'pathname')]
)
def update_page_content(pathname):
if pathname == '/':
return 'This is the home page!'
elif pathname == '/about':
return 'This is the about page!'
else:
return '404 Error!'
if __name__ == '__main__':
app.run_server(debug=True)
Explanation:
-
dcc.Location: Thedcc.Locationcomponent is the key to our goal. It captures the current URL and provides an input for our callback. -
Callback Function: We use a callback to dynamically update the
page-contentdiv based on the current pathname provided bydcc.Location. This is where the logic for generating the HTML content for each page resides. -
HTML Output: In the callback function, we return a string that represents the desired HTML content. This could be text, components, or even full-fledged layouts.
How to Generate the Standalone HTML:
-
Run the app: Start the Dash app as usual.
-
Navigate to desired URL: Open the app in your web browser and visit the specific page you want to export (e.g.,
/about). -
Inspect the page: Right-click on the page and choose "Inspect" (or use your browser's developer tools).
-
Find the
dcc.Locationelement: Locate the element with the id "url" in the "Elements" tab of your browser's developer tools. -
Copy the generated HTML: Copy the HTML code displayed in the "Elements" tab. This code will contain the layout of your app, along with all necessary JavaScript and CSS files.
-
Save the HTML file: Paste the copied HTML code into a new file and save it with a
.htmlextension. This is your standalone HTML file.
Important Points:
-
Dependencies: If your app uses external libraries like Plotly, ensure that you include the corresponding JavaScript and CSS files in the standalone HTML. This can be done by adding
<script>and<link>tags to the<head>section. -
Data: The data for your visualizations and other components will be embedded within the HTML file. If you're working with large datasets, consider optimizing your code for efficient data loading and rendering.
-
Deployment: After creating the standalone HTML file, you can easily share it with others or embed it in other websites.
Conclusion:
By leveraging the power of dcc.Location and a few lines of code, Dash allows you to transform your interactive dashboards into standalone HTML files. This opens up possibilities for wider distribution and seamless integration with other platforms.
