how to save a file outside the docker container with python [duplicate]

Question

So I have this structure:

myapp

Dockerfile
main.py
req.txt

this is the content of my Dockerfile:

FROM python:3.8
ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1
COPY . /app
WORKDIR /app
RUN pip3 install -r req.txt
RUN playwright install
RUN playwright install-deps

CMD ["python", "./main.py"]

and on my main.py, eventually, I have this code

 current_path = os.path.dirname(os.path.abspath(__file__))
 result_path = os.path.join(current_path, 'result.json')

 with open(result_path, 'w') as json_file:
    json.dump(result, json_file, indent=4)

I can see that the script is running successfully, but I can't see the file that was supposed to be created in the same folder, I understand that the file is being created at

/app/results.json

but there's a way for this file to be created outside the container?

EDIT: I have done my build with:

docker build -t myapp .

and I run like this:

docker run myapp

Suchandra T · Accepted Answer · 2023-05-22 04:58:36Z

2

So far so good, the way you are running app is perfectly alright.

So in Docker to save files on host's file system theres is a concept called mounting the volume from which file or directory of host can be directly mounted to your running container.

So right now I do not know where you want that file to be written on host. but the general command will be like this:

docker run -v app:/app -it myapp

This mounts app folder of your host to app folder in the container

More read on the same topic: https://docs.docker.com/storage/bind-mounts/

Hope this helps. Thanks.

answered May 22, 2023 at 4:58

Suchandra T

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Yum Lee · Accepted Answer · 2023-05-22 05:04:22Z

2

Use bind mount at docker run:

docker run -v /path/to/host_app_dir:/app  myapp

This will bind two directories: the /path/to/host_app_dir in your host system and the /app folder inside docker. Any file written to /app will appear in /path/to/host_app_dir. They are essentially the same folder on your hard disk. That is the magic of bind mount.

Be careful, because you copy something into the /app folder (COPY . /app) during docker build. The content of /app will be replaced by the content of your host folder using the bind mount option above. See the documentation.

I suggest that you use a different folder instead of /app to share files between the host and container.

edited May 22, 2023 at 5:04

answered May 22, 2023 at 4:57

Yum Lee

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FordPrefect · Accepted Answer · 2023-05-22 04:58:17Z

0

You need to mount bind a folder on your machine to a folder inside the container with the-v option. Files created inside this folder are then outside of the container.

answered May 22, 2023 at 4:58

FordPrefect

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