Run Python script without web server into Docker?

Question

I have been working with Docker previously using services to run a website made with Django.

Now I would like to know how I should create a Docker to just run Python scripts without a web server and any service related with websited.

An example of normal docker which I am used to work is:

version: '2'
services:
  nginx:
    image: nginx:latest
    container_name: nz01
    ports:
      - "8001:8000"
    volumes:
      - ./src:/src
      - ./config/nginx:/etc/nginx/conf.d
    depends_on:
      - web
  web:
    build: .
    container_name: dz01
    depends_on:
      - db
    volumes:
      - ./src:/src
    expose:
      - "8000"
  db:
    image: postgres:latest
    container_name: pz01
    ports:
        - "5433:5432"
    volumes:
      - postgres_database:/var/lib/postgresql/data:Z
volumes:
    postgres_database:
        external: true

How should be the docker-compose.yml file?

Thomas Kainrad · Accepted Answer · 2019-03-04 15:51:58Z

5

Simply remove everything from your Dockerfile that has nothing to do with your script and start with something simple, like

FROM python:3

ADD my_script.py /

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

You do not need Docker compose for containerizing a single python script.

The example is taken from this simple tutorial about containerizing Python applications: https://runnable.com/docker/python/dockerize-your-python-application

You can easily overwrite the command specified in the Dockerfile (via CMD) when starting a container from the image. Just append the desired command to your docker run command, e.g:

docker run IMAGE /path/to/script.py

edited Mar 4, 2019 at 15:51

answered Mar 4, 2019 at 13:56

Thomas Kainrad

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2 Comments

mrc Over a year ago

what about making the CMD exec variable? For example if you want to call different python script every time? You can ADD the folder I know, but how to make the CMD filename variable of a input for example?

Thomas Kainrad Over a year ago

Just overwrite the CMD when starting the container, I added a short explanation to my answer.

Stuart Buckingham · Accepted Answer · 2019-03-04 14:21:03Z

2

You can easily run Python interactively without even having to build a container:

docker run -it python

If you want to have access to some code you have written within the container, simply change that to:

docker run -it -v /path/to/code:/app: python

Making a Dockerfile is unnecessary for this simple application.

answered Mar 4, 2019 at 14:21

Stuart Buckingham

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5 Comments

mrc Over a year ago

is the path until the folder, or even the script name? I made it using the filename and it opens the STDIN but it doesn't print the script result.

Stuart Buckingham Over a year ago

The path is just the path to 'mount' to. To actually execute the code (say you have a script in the local directory /my_app/test_script.py, the command would be: docker run -v /my_app:/my_app: python python /my_app/test_script.py. The first 'python' is the name of the container, and 'python /my_app/test_script.py' is the command to be run.

mrc Over a year ago

Okey, the thing is that I get an error of mounts denied. The path is not shared 'Desktop/src' but it is under 'users/' which is already shared in docker preferences.

mrc Over a year ago

Already working :) Thanks a lot! The last issue was related with relative and full path. I was using relative path, and it should be full.

Stuart Buckingham Over a year ago

No problem. If this has helped you, please upvote. If it solved your problem, please accept it so the answer.

David Maze · Accepted Answer · 2019-03-04 15:09:19Z

0

Most Linux distributions come with Python preinstalled. Using Docker here adds significant complexity and I'd pretty strongly advise against Docker just to run a simple script. You can use a virtual environment to isolate a particular Python package's dependencies from the rest of the system.

(There is a pretty consistent stream of SO questions around getting filesystem permissions and user IDs right for scripts that principally want to interact with the host system. Also remember that running docker anything implies root-equivalent permissions. If you don't want Docker's filesystem and user namespace isolation, IMHO it's easier to just not use Docker where it doesn't make sense.)

answered Mar 4, 2019 at 15:09

David Maze

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