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What's a good way to calculate the execution time for every page load using Python's Flask library?
I was thinking of putting a start timer in views/__ init__.py:
@app.before_request
def before_request():
g.start = time.time()
But where would I put the end part of the timer to calculate the difference, and how would I get it into the footer of my html template?
Thanks.
257
Put it in teardown_request function:
@app.teardown_request
def teardown_request(exception=None):
diff = time.time() - g.start
...
In teardown_request you are not allowed to change the response, If you want to use the calculated string in your response use after_request:
@app.after_request
def after_request(response):
diff = time.time() - g.start
if (response.response):
response.response[0] = response.response[0].replace('__EXECUTION_TIME__', str(diff))
return response
The other answers are essentially correct, but quite out of date now.
The following works with Python 3.6 / 3.7 and Flask 1.0.2:
import time
from flask import g
@app.before_request
def before_request():
g.start = time.time()
@app.after_request
def after_request(response):
diff = time.time() - g.start
if ((response.response) and
(200 <= response.status_code < 300) and
(response.content_type.startswith('text/html'))):
response.set_data(response.get_data().replace(
b'__EXECUTION_TIME__', bytes(str(diff), 'utf-8')))
return response
By using response.set_data, the content-length will be correctly updated by Flask. Please also note the use of byte strings and the encoding.
33
You also need to update the content-length header otherwise browsers get upset (and Chrome seems to give unpredictable results).
@app.after_request
def after_request(response):
diff = time.time() - g.start
if app.debug:
print "Exec time: %s" % str(diff)
if (response.response):
response.response[0] = response.response[0].replace('__EXECUTION_TIME__', str(diff))
response.headers["content-length"] = len(response.response[0])
return response
Try out this: https://code-maven.com/flask-display-elapsed-time
import time
from flask import Flask, request, render_template, g
app = Flask(__name__)
@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 main():
return render_template('main.html')
and template html like:
<html>
<head>
</head>
<body>
<h1>Show elapsed time</h1>
<hr>
Elapsed time: {{ g.request_time() }}
</body>
</html>
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