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How to Efficiently Stream Real-time Data from a Flask View into an HTML Template?
How to Efficiently Stream Real-time Data from a Flask View into an HTML Template?
Dec 26, 2024 pm 12:55 PM
Streaming Data into an HTML Template
When working with real-time data streamed from a Flask view, it's natural to want to display it in a dynamic HTML template. However, traditional template rendering techniques fall short as the template is rendered once on the server-side and sent in its entirety to the client.
Using JavaScript for Dynamic Display
One solution to this issue is to utilize JavaScript for client-side updates. By making an XMLHttpRequest request to the streaming endpoint, you can read the data incrementally and output it directly to the page. This approach allows for real-time updates and complete control over the display format.
Here's an example using JavaScript:
Python (server-side):
from flask import Flask, Response
app = Flask(__name__)
@app.route('/')
def index():
return render_template('index.html')
@app.route('/stream')
def stream():
def generate():
for i in range(10):
yield str(i) + '\n'
return Response(generate(), mimetype='text/plain')
HTML (client-side):
<p>This is the latest output: <span>
Using an Iframe for HTML Streaming
An alternative approach involves using an iframe to display streamed HTML output. While this technique allows for dynamic rendering, it comes with drawbacks:
- Adds complexity due to separate document context
- Limited styling options
- Potential rendering issues with long output
In this method, the index.html file would contain:
<p>This is all the output:</p>
<iframe src="{{ url_for('stream') }}"></iframe>
And the stream view in Python would be:
from flask import stream_with_context
@app.route('/stream')
def stream():
@stream_with_context
def generate():
yield '<link rel=stylesheet href="{{ url_for('static', filename='stream.css') }}">'
for i in range(10):
yield render_template_string('<p>{{ i }}: {{ s }}</p>\n', i=i, s=sqrt(i))
In this example, CSS is loaded first in the iframe using render_template_string, and the HTML content is streamed incrementally.
The above is the detailed content of How to Efficiently Stream Real-time Data from a Flask View into an HTML Template?. For more information, please follow other related articles on the PHP Chinese website!
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