I have have a container running postgresql and I want to ingest there some data that I have prepared in a ETL script. I have created the database, however, When I try to connect in my local machine through a jupyter notebook, it keeps saying it cannot find the host, even though I set it in my .yaml file.
My .yaml file is this one:

version: '3.7'
services:
  postgres:
    image: library/postgres
    container_name: postgres_db
    restart: unless-stopped
    ports:
      - 5432:5432
    environment:
      - POSTGRES_PASSWORD=password123
      - POSTGRES_USER=user123
      - POSTGRES_DB=my_db
    hostname: postgres
    volumes:
      - ./pgdata/data:/var/lib/postgresql/data
      - ./initdb:/docker-entrypoint-initdb.d
    

In my jupyter notebook I have this connection test:

import psycopg2

DATABASE_HOST = 'postgres'  
DATABASE_PORT = 5432
DATABASE_USER = 'user123'
DATABASE_PASSWORD = 'password123'
DATABASE_NAME = 'my_db'

conn = psycopg2.connect(
        host=DATABASE_HOST,
        port=DATABASE_PORT,
        user=DATABASE_USER,
        password=DATABASE_PASSWORD,
        dbname=DATABASE_NAME
    )

The logs on docker side never come back with any type of connection attempt.

OperationalError: could not translate host name "postgres" to address: Unknown host