ubuntu 18.04 serverpsql: error: could not connect to server: Connection refused Is the server running on host "db01.localhost" (127.0.0.1) and accepting TCP/IP connections on port 5432? code example

Example: psycopg2.OperationalError: could not connect to server: Connection refused Is the server running on host "127.0.0.1" and accepting TCP/IP connections on port 5432?

# to over ride this error you should up and run server
service postgresql start