Flask - Webserver not reloading on code change

Question

For some reason, 127.0.0.1:5000(port 5000) is stuck displaying my old un-updated file.

from flask import Flask
app = Flask(__name__)

@app.route("/")
def index():
    return "Home page"

@app.route("/about")
def about():
    return "About page"

if __name__ == "__main__":
    app.run()

I changed the port and it worked fine. But, why is 5000 not updating when I change and run my code? I checked to see if multiple process were running, but none were.

Honestly, this is a noob question, but I can't seem to find anyone else who's had this problem.

What do you see if you run these commands: `$ telnet localhost 5000` and `$ ps aux | grep 5000` — JacobIRR, Sep 01 '17 at 21:28
Thank you, but I actually resolved the issue. Yes, it was running somewhere. I `statnet -a -b` in command and found python was still listening on port 5000. So, I just ended the task. Now, my question is, how was it still listening if I manually decide when to run and end the server? — Bryan Hinchliffe, Sep 01 '17 at 21:43
@BryanHinchliffe, I know this is quite old but I am having the same issue. How did you manage to solve the issue? I am working in a windows computer and Pycharm. Thanks — Ana, Jun 25 '21 at 08:01
@Ana Sorry for the late response. I'm assuming you resolved this issue by now, but if it helps, I had to manually kill the Python process running on port 5000. You can use [this](https://stackoverflow.com/questions/39632667/how-do-i-kill-the-process-currently-using-a-port-on-localhost-in-windows) answer (option 2) to find and kill process. Hope this helps! — Bryan Hinchliffe, Aug 24 '21 at 21:10
@BryanHinchliffe. Thanks. I resolved this by disconnected the computer, and stopped running everything. I tried all the answers in the post but none worked. — Ana, Sep 07 '21 at 16:00

score 12 · Answer 1 · edited Mar 21 '23 at 13:02

12

Press CTR + C to end your server on the terminal and copy and paste this in the terminal to run Flask again

export FLASK_DEBUG=1 && flask run

This will set Debug mode: on

edited Mar 21 '23 at 13:02

Alexey Nikonov

4,958
5
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answered Oct 09 '19 at 06:20

kingnanaprempeh

137
1
4

2

The term 'FLASK_DEBUG=1' is not recognized as the name of a cmdlet – Kitwradr Jan 20 '20 at 09:24
fixed issue with not recognized name – Alexey Nikonov Mar 21 '23 at 13:02

score 8 · Answer 2 · answered Jan 24 '20 at 08:59

8

To set variable in powershell -

$env:FLASK_DEBUG=1

answered Jan 24 '20 at 08:59

user2959786

101
1
2

score 7 · Answer 3 · answered Sep 04 '17 at 09:35

7

No! You have not run your app in debug mode.

app.run(debug=True)

This way any changes in your code will restart the server and your code changes will reflect pretty much in real time.

answered Sep 04 '17 at 09:35

Nabin

11,216
8
63
98

score 4 · Answer 4 · answered Mar 31 '21 at 19:44

4

I don't know why this happens. Other answer didn't help. Community should help.

Other Two options:

If you are using Visual Studio Code, Close and Open it.
Uninstall and install python again.

answered Mar 31 '21 at 19:44

Shaiju T

6,201
20
104
196

2

Restarting VSCode worked for me, thank you! – Georges D Jun 25 '21 at 09:48
1

I had the same problem, I am using sublime text, closing and opening it worked thx! – Chami Mohammed Aug 26 '22 at 12:37

score 3 · Answer 5 · answered Jan 13 '22 at 15:14

To anyone still struggling with this issue while having debug=True correctly passed to app.run(), Flask (2.0.x) documentation states that :

debug=True can be passed to enable the debugger and reloader, but the FLASK_ENV=development environment variable is still required to fully enable development mode

See https://flask.palletsprojects.com/en/2.0.x/server/

So you should also run your development server with export FLASK_ENV=development before flask run.

score 2 · Answer 6 · answered Jan 16 '23 at 07:01

2

flask --app <.py file name> --debug run

answered Jan 16 '23 at 07:01

Pasindu Madushan

21
1

score 1 · Answer 7 · answered Mar 31 '21 at 07:21

1

Reload the page using Shift+ F5. But make sure app should be in debug mode i.e. app.run(debug=True).

answered Mar 31 '21 at 07:21

Dhruv

13
7

score 0 · Answer 8 · answered Feb 29 '20 at 18:09

0

If you are using the built-in app.run() try adding app.run(debug=True) It solves.

answered Feb 29 '20 at 18:09

Ish

113
7

score 0 · Answer 9 · answered Aug 16 '21 at 18:04

0

Somehow the Flask server froze. For me the solution was to kill the pythonw.exe process in the task manager.

answered Aug 16 '21 at 18:04

hlorand

1,070
10
8

score 0 · Answer 10 · answered Jan 01 '22 at 04:01

0

For me, running these three commands took care of the reloading problem (windows machine):

$env:FLASK_APP = "main.py"
$env:FLASK_DEBUG = 1
flask run

answered Jan 01 '22 at 04:01

Sadman Sakib

557
3
10

score 0 · Answer 11 · answered Apr 08 '22 at 01:59

My issue was that another application (Proton Mail Bridge) was listening on the same port (5000) my Flask app was, however no error was thrown. If you are on Windows, I would try running netstat -ab in CMD after opening as an administrator and see if any applications are listening to the same port your flask app is running on.

4.5 years later I know, but I could not find any answers on this earlier.

Flask - Webserver not reloading on code change

11 Answers11