Sometime there is some code that you would like to run after the requests was served. The after_request hook can help you in this, thoigh beware, it won't run in the rare (well, hopefully rare) cases when there is an uncaught exception in the route.

examples/flask/after_request/app.py

from flask import Flask, abort
import datetime

app = Flask(__name__)

@app.after_request
def after_request(response):
    app.logger.info("after_request")
    return response

@app.route("/")
def main():
    app.logger.info("main route")
    return "Hello " + str(datetime.datetime.now())

@app.route("/crash")
def crash():
    app.logger.info("crash route")
    a = 0
    b = 3 / a

Run as: 

FLASK_APP=app FLASK_DEBUG=1 flask run

Output on the console: 

[2020-06-23 13:21:22,699] INFO in app: main route
[2020-06-23 13:21:22,699] INFO in app: after_request
127.0.0.1 - - [23/Jun/2020 13:21:22] "GET / HTTP/1.1" 200 -

Visiting the http://localhost:5000/crash URL shows a stack trace like this: 

[2020-06-23 13:21:11,582] INFO in app: crash route
127.0.0.1 - - [23/Jun/2020 13:21:11] "GET /crash HTTP/1.1" 500 -
Traceback (most recent call last):
  ...
  File "/home/gabor/work/code-maven.com/examples/flask/after_request/app.py", line 20, in crash
    b = 3 / a
ZeroDivisionError: division by zero