Can not connect PostgreSQL database from docker to python

Question

I am trying to use Postgresql with python. I have used the following docker compose the file.

version: '3.1'

services:

  db:
    image: postgres
    restart: always
    environment:
      POSTGRES_PASSWORD: admin_123
      POSTGRES_USER: admin

  adminer:
    image: adminer
    restart: always
    ports:
      - 8080:8080

With the following code, I am trying to connect with the database.

conn = psycopg2.connect(
    database = "db_test",
    user ="admin",
    password = "admin_123",
    host = "db"
)

But I am getting this error.

OperationalError: could not translate host name "db" to address: nodename nor servname provided, or not known

What I am doing wrong ?

Answer 1

You need to expose the BD port in the docker compose like this :

db:
image: postgres
restart: always
environment:
  POSTGRES_PASSWORD: admin_123
  POSTGRES_USER: admin
ports:
    - "5432:5432"

And then connect with localhost:5432

Answer 2

Another possible scenario,

Check if ports have been used or not by other docker container. Use command:

$ docker container ls --format "table {{.ID}}\t{{.Names}}\t{{.Ports}}" -a

Answer 3

Here is my docker-compose.yml

$ cat docker-compose.yml

version: '3.1' # specify docker-compose version
services:
  dockerpgdb:
    image: postgres
    ports:
      - "5432:5432"
    restart: always
    environment:
      POSTGRES_PASSWORD: Password
      POSTGRES_DB: dockerpgdb
      POSTGRES_USER: abcUser
    volumes:
      - ./data:/var/lib/postgresql%

Now in PgAdmin4 you can setup a new server as below to test the connection:

host: localhost
port: 5432
maintenance database: postgres
username: abcUser
password: Password