How two diffrent docker container api communicate with each other requests?

version : '3.4'

services:
 UI:
  container_name: django_app
  image: django_image
  networks:
   my_net:
    ipv4_address: 172.26.1.1
  ports:
   - "8080:8000"
 api:
  container_name: flask_app
  image: flask_image
  networks:
   my_net:
    ipv4_address: 172.26.1.2

networks:
 my_net:
  ipam:
   driver: default
   config:
    - subnet: 172.26.0.0/16