Flask Static Progress Screen

Question

Option 1: No Javascript

I just want to display a static template that says \'please wait...\' while a task is running. Here is a simplified version of the

Answer 1

You can stream a response to get a very simple progress report. See the docs on streaming for more information. This example outputs a percent complete while waiting 5 seconds. Rather than sleeping, you would be processing csv or whatever you need to do.

from flask import Flask, Response
import time

app = Flask(__name__)

@app.route('/')
def index():
    def generate():
        yield 'waiting 5 seconds\n'

        for i in range(1, 101):
            time.sleep(0.05)

            if i % 10 == 0:
                yield '{}%\n'.format(i)

        yield 'done\n'

    return Response(generate(), mimetype='text/plain')

app.run()

This outputs the following over 5 seconds:

waiting 5 seconds
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
done

This isn't very complex, but it's also just plain text. A much more powerful solution would be to run the task in the background using Celery and poll it's progress using ajax requests.