How to Dynamically Display Streaming Flask Data in an HTML Template?

Dynamically Displaying Streaming Data in a Flask Template

In web development, it is common to display data that is constantly updated, such as real-time data streams. With Flask, a popular Python web framework, it may seem challenging to handle this type of data in your HTML templates. This question delves into how to effectively display streaming data and incorporate it into your templates.

Problem Statement

The given Flask application generates data and streams it in real time through a specific endpoint. The question arises: how to access this streamed data within an HTML template and display it with formatting?

Solution

While the application sends data as a stream, updating a template dynamically based on this stream is not possible. Instead, the data must be handled on the client side using JavaScript.

JavaScript Implementation

The example provided demonstrates using JavaScript to handle the streamed data:

1. Use XMLHttpRequest to open a connection to the streaming endpoint.
2. Read from the stream periodically, handling each message (line of data).
3. Update the display with the latest value and log all messages.

HTML Template

The HTML template includes the JavaScript code and provides areas to display the data:

<p>This is the latest output: <span></span></p>

Alternative Approach: Using an Iframe

Another option for displaying streaming data is to use an iframe. An iframe serves as a separate document within the main page, displaying content from a different URL. In this case, the iframe can point to the streaming endpoint and display the streamed HTML data.

Benefits and Drawbacks

The iframe approach provides a straightforward way to display streamed HTML, but it has drawbacks such as increased resource usage and styling limitations. It's generally preferred to use JavaScript and direct manipulation of the page for greater flexibility.

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