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 ?

Possible duplicate of docker-compose: difference between network and link — awesoon
– awesoon, Commented Feb 10, 2019 at 14:54
how ? would you please explain ? I read that but not getting it — TheTechGuy
– TheTechGuy, Commented Feb 10, 2019 at 15:01
Where is your Python code running; on the host or in a container? If in a container, how did you start it? — David Maze
– David Maze, Commented Feb 10, 2019 at 15:15
Sorry, this link is probably irrelevant here. I thought you are trying to access db inside adminer, is it correct? — awesoon
– awesoon, Commented Feb 10, 2019 at 15:19

Zak · Accepted Answer · 2019-02-10 16:04:19Z

7

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

answered Feb 10, 2019 at 16:04

Zak

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Comments

Alphapico · Accepted Answer · 2020-05-12 07:31:37Z

1

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

answered May 12, 2020 at 7:31

Alphapico

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Comments

AvkashChauhan · Accepted Answer · 2020-05-24 18:00:24Z

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

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