This question probably needs some work to clarify your use case, but I'll answer as best as I can.

Generally, containers orchestrated in compose are all hosted on the same network, by default host networking. So, all should need to do is have a Dockerfile for each of your python projects, expose a port, connect them with docker compose, and perform your communication over these ports. These ports should map to ports on your host OS. e.g. a web app running on port 3000 in a docker-compose container will be available on your localhost at 3000.

Say you have a project structure like this:

.
├── docker-compose.yml
├── project1
│   ├── Dockerfile
│   └── main.py
└── project2
    ├── Dockerfile
    └── main.py

Then you could have a project1/Dockerfile like this:

#whatever python you need
FROM godatadriven/python-onbuild 

# Coping source in current directory into the image
COPY . /app

#whatever your project needs to work 
RUN pip install --upgrade pip 
RUN pip install -r requirements.txt 

# Commands in a list
CMD ["python", "main.py"]

# Expose web port
EXPOSE 8002/tcp 

And something similar for project2/Dockerfile. Then, your docker-compose.yml would contain something like:

version: '3.9'  # version of compose format 

services:
  project1:
    build: ./project1  # path is relative to docker-compose.yml location
    volumes:
      - ./project1:/app # mount point
    #specify resources for container - you may not need to
    deploy:
      resources:
        limits:
          memory: 500M
        reservations:
          memory: 100M
    ports:
      - 8002:8002  # host:container
  project2:
    build: ./project2
    volumes:
      - ./project2:/app # mount point
    deploy:
      resources:
        limits:
          memory: 500M
        reservations:
          memory: 100M
    ports:
      - 8001:8001  # host:container

Then, you need to send all communication that these python projects are doing over these ports.

You would probably benefit from reading through Dockerfile best practices and Docker Compose docs. This will be an easy base image to start with, but you'll need to explore this and find out exactly what you need. In general, stay away from Alpine linux as you'll get crappy build times.