flask: show request time in template

app.py

import time

from flask import Flask, request, g, render_template

app = Flask(__name__)
app.config['DEBUG'] = True

@app.before_request
def before_request():
    g.request_start_time = time.time()
    g.request_time = lambda: "%.5fs" % (time.time() - g.request_start_time)

@app.route("/")
def index():
    t = request.values.get('t', 0)
    time.sleep(float(t)) #just to show it works...
    return render_template("index.html")

if __name__ == "__main__":
    app.run(use_debugger=True, use_reloader=True)

index.html

Rendered in {{ g.request_time() }}

output.txt

$ curl http://127.0.0.1:5000/
Rendered in 0.00100s

$ curl http://127.0.0.1:5000/?t=1
Rendered in 1.00106s

$ curl http://127.0.0.1:5000/?t=2
Rendered in 2.00111s

$ curl http://127.0.0.1:5000/?t=10
Rendered in 10.00057s

Great, didn't know there's such thing as before_request and after_request, thank you :)

Cool solution, just one small thing to pay attention to when your measuring performance:

If you call {{ g.request_time() }} at the start of your html template, and then do a whole bunch of rendering, the time will be off. I had up to a factor of 20x speed difference, and couldn't figure out why, and this was the reason. My solution was to put this small snippet at the button of the template:

...

<p id="request_time_paragraph"></p>

do_some_heavy_rendering()
<script>
document.getElementById('request_time_paragraph').innerHTML = "{{ g.request_time() }}"
</script>

You’ll want to use time.monotonic() for correctness :)

Otherwise, you end up with weird negative page rendering times during leap seconds :)

I got jinja2.exceptions.TemplateNotFound

please resolve this

@mallikharjuna160003 To resolve this error just create a directory "templates" and put the required html files in.