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](https://stackoverflow.com/questions/41294305/docker-compose-difference-between-network-and-link) — awesoon, Feb 10 '19 at 14:54
how ? would you please explain ? I read that but not getting it — TheTechGuy, Feb 10 '19 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, Feb 10 '19 at 15:15
Sorry, this link is probably irrelevant here. I thought you are trying to access `db` inside `adminer`, is it correct? — awesoon, Feb 10 '19 at 15:19
@TheTechGuy Are you trying to connect to the database from your host machine? — Zak, Feb 10 '19 at 15:55
yes, the same machine where the docker is running , I just need to insert data to the database. The database is running in Docker. and I have a Jupyter notebook with that I am trying to connect. While I am trying to connect i got the mentioned error. — TheTechGuy, Feb 10 '19 at 16:01

score 7 · Accepted Answer · answered Feb 10 '19 at 16:04

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 '19 at 16:04

Zak

1,005
10
22

score 1 · Answer 2 · answered May 12 '20 at 07:31

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 '20 at 07:31

Alphapico

2,893
2
30
29

score 0 · Answer 3 · answered May 24 '20 at 18:00

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

Can not connect PostgreSQL database from docker to python

3 Answers3