Docker-compose IP address for Database

Don't use ip addresses from within containers. Instead use the links flag to connect multiple containers together, then use the linked container's name.

version: "3"

services:
  db:
    image: postgres
    volumes:
      - ./data/db:/var/lib/postgresql/data
    environment:
      - POSTGRES_DB=postgres
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres
  web:
    build: .
    command: python manage.py runserver 0.0.0.0:8000
    volumes:
      - .:/code
    ports:
      - "8000:8000"
    depends_on:
      - db
    links:
      - db

The link allows the web container to reach the db container with the hostname db.