docker-compose up is a foreground starting (stdin capturing, stdout printing ... and waiting for the exiting command/signal)

For you case, more suitable is background starting (`docker compose up -d', see d(detached) flag). This command starts the container and give the control to next command (attaching).

UPDATE:

If background running does not help, try run in background and this solution.

Finally i managed to solve it myself. Few takeaways from the problem.

You need to use debugpy and place that in your manage.py file to start listening to a port. I did something like this

import debugpy

debugpy.listen(('0.0.0.0', 5678))
debugpy.wait_for_client()
debugpy.breakpoint()

Along with this we need to map this port to a port inside the host machine. For that we need to change and add a single line in web service of docker-compose

ports:
    - "5678:5678"

And my launch.json looks like this

{
"configurations": [
    {
        "name": "Python: Remote Attach",
        "type": "python",
        "request": "attach",
        "connect": {
            "host": "0.0.0.0",
            "port": 5678
        },
        "pathMappings": [
            {
                "localRoot": "${workspaceFolder}/myapp",
                "remoteRoot": "."
            }
        ]
    }
]
}

NOTE: make sure you have debugpy in your requirements file or install it manually.

Yes, this is possible - when the Python app is running in a Docker container, you can treat it like a remote machine.

In your Docker image, you'll need to make the remote debugging port available (e.g. EXPOSE 3000 in the Dockerfile), include the ptvsd setup in your Python app, and then publish the port when you run the container, something like:

docker run -d -p 3000:3000 my-image

Then use docker inspect to get the IP address of the running container, and that's what you use for the host in the launch file.

I finally got it working with remote debugging. I had to pip3 install ptvsd==3.0.0 on my local, and make sure that the requirements.txt for my docker container had the same version. (note: the latest version 3.2.1 didn't work)

@BrettCannon had the right link for a good tutorial https://code.visualstudio.com/docs/python/debugging#_remote-debugging

What I had to do was add some code to the app.py of the flask app. I originally was getting address already in use error when starting the container, so I added the socket code and after the first successful attach of debugger I didn't seem to need it anymore (strange I know, but that's why I left it in in case someone else gets that error)

try:
    import ptvsd
    # import socket
    # sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    # sock.close()
    ptvsd.enable_attach(secret=None,address=('0.0.0.0',5050))
    ptvsd.wait_for_attach()
except Exception as ex:
    print('Not working: ')

also i took the debug kwarg off the app.run() in app.py for the flask app. This all gave me the ability to connect the debugger, but the breakpoints where "Unverified", so the last thing that had to happen was a path to the app.py in the launch.json for the remoteRoot. I will say I created a small test api to get this working, and it only need the first level of pathing (ie. /app and not /app/app/app.py)Here is a github of the test api I made (https://github.com/tomParty/docker_python). So if the debugger is attaching, but your breakpoints are unverified, play around with the path of the remoteRoot

"remoteRoot": "/nomz/nomz/app.py"