import paramiko
ssh_client =paramiko.SSHClient()
ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
sh_client.connect(hostname='<IP>', username='root', password='<passwd>')

stdin, stdout, stderr = ssh_client.exec_command('su - service_user')
stdin, stdout, stderr = ssh_client.exec_command('whoami')
stdout.readlines()