Ejemplo básico de conexión a postgres con python sobre contenedores docker

app.py

# docker run --name some-postgres -p 5432:5432 -e POSTGRES_PASSWORD=postgres -tid postgres:12.0
# docker run -v C:\Users\Datasoft\Desktop\py:/script --rm python:3.7  bash -c "pip install psycopg2 && python /script/app.py"
import psycopg2
try:
    connection = psycopg2.connect(user = "postgres",
                                  password = "postgres",
                                  host = "192.168.1.40",
                                  port = "5432",
                                  database = "postgres")

    cursor = connection.cursor()
    # Print PostgreSQL Connection properties
    print ( connection.get_dsn_parameters(),"\n")

    # Print PostgreSQL version
    cursor.execute("SELECT version();")
    record = cursor.fetchone()
    print("You are connected to - ", record,"\n")

except (Exception, psycopg2.Error) as error :
    print ("Error while connecting to PostgreSQL", error)
finally:
    #closing database connection.
        if(connection):
            cursor.close()
            connection.close()
            print("PostgreSQL connection is closed")