command/CMD in docker-compose is not equivalent to CMD in Dockerfile

I have a container that uses a volume in its entrypoint. for example

CMD bash /some/volume/bash_script.sh

I moved this to compose but it only works if my compose points to a Dockerfile in the build section if I try to write the same line in the command section is not acting as I expect and throws file not found error.

I also tried to use docker-compose run <specific service> bash /some/volume/bash_script.sh which gave me the same error.

The question is - Why dont I have this volume at the time that the docker-compose 'command' is executed? Is there anyway to make this work/ override the CMD in my dockerfile?

EDIT: I'll show specifically how I do this in my files:

docker-compose:

version: '3'
services:
  base:
    build: 
      context: ..
      dockerfile: BaseDockerfile
    volumes:
      code:/volumes/code/
  my_service:
    volumes:
      code:/volumes/code/
    container_name: my_service
    image: my_service_image
    ports:
      - 1337:1337
    build: 
      context: ..
      dockerfile: Dockerfile

volumes: code:

BaseDockerfile:

FROM python:3.6-slim

WORKDIR /volumes/code/

COPY code.py code.py
CMD tail -f /dev/null

Dockerfile:

FROM python:3.6-slim

RUN apt-get update && apt-get install -y redis-server \
alien \
unixodbc 

WORKDIR /volumes/code/


CMD python code.py;

This works.

But if I try to add to docker-compose.yml this line:

command: python code.py

Then this file doesnt exist at the command time. I was expecting this to behave the same as the CMD command