Running a simple Flask app will not work because an older run is cached somehow.

[enjoysmath]

Expected Behavior

For updates of the code including favicon and index.html to be shown when I hit run in my IDE again (Wingware, but same problem at command line).

# Minimal example is any Flask app

Actual Behavior

Running the app renders the same app I first ran today, namely:
https://github.com/helloflask/calculator

Changing the page title in index.html or the favicon does not get reflected when the app is run.

Environment

• Python version: Python 3.8.3
• Flask version: Version: 1.1.2
• Werkzeug version: Version: 1.0.1

---

I've made the following script in order to try to both kill the server and delete any .pyc caching that might be causing the problem. For Windows only:

kill_server.py:

import os
import subprocess
import re

port = 5000
host = '127.0.0.1'
cmd_newlines = r'\r\n'

host_port = host + ':' + str(port)
pid_regex = re.compile(r'[0-9]+$')

netstat = subprocess.run(['netstat', '-n', '-a', '-o'], stdout=subprocess.PIPE)  
# Doesn't return correct PID info without precisely these flags
netstat = str(netstat)
lines = netstat.split(cmd_newlines)

for line in lines:
    if host_port in line:
        pid = pid_regex.findall(line)
        if pid:
            pid = pid[0]
            os.system('taskkill /F /PID ' + str(pid))
        
# And finally delete the .pyc cache
os.system('del /S *.pyc')

The problem remains dispite manually doing the above taskkills and deleting .pyc files by hand or running kill_server.py. Therefore, there's something going on in Flask that is causing the old app to be run (it's cached or something...)

Please help! I really want to make a calculator in Flask, not CherryPy.

I've tried "Clear Browsing Data > Clear Images & Files / Cookies" in Chrome, on Windows 10. Same issue.

[enjoysmath]

Okay, maybe clear browsing data did work, because it's showing the new favicon now. But it didn't work immediately after doing that. Anyhow... thanks for any advice you have.

[davidism]

It's a browser caching issue. Better defaults will be used in Flask 2.0 with pallets/werkzeug#1886.