Why do I get the error "python: can't open file '//temp/hello_world.py': [Errno 2] No such file or directory" when running an image?

Question

Python

docker-compose.yml :

version: '3.9'
services:
  python_runner:
    build:
       context: ./compilers/python
       dockerfile: Dockerfile
    volumes:
       - ./temp:/temp 
    container_name: python_runner_container 
    environment:
      - FILENAME=${FILENAME}

  java_runner:
    ...

Dockerfile to run python :

FROM python
ARG FILENAME_ARG
ENV FILENAME = $FILENAME_ARG
CMD python temp/${FILENAME}

First, I go to the c folder docker-composeand run it with the command:
docker-compose up -d

Then I try to run the image that executes python:

docker run --env FILENAME=hello_world.py compilers_python_runner

But in the output I get an error:

python: can't open file '//temp/hello_world.py': [Errno 2] No such file or directory

Interestingly, when I run through the PyCharmdocker-compose interface and manually set the value of the variable , everything works correctly. What is the error and how to fix it? FILENAME