I was trying to connect oracle database using python like below.
import cx_Oracle
conn = cx_Oracle.connect(\'user/password@host:port/database\')
This error come when your Oracle Client is not installed or LD_LIBRARY_PATH is not set where libclntsh.so is present.
if you have Oracle client installed then search for libclntsh.so and set the LD_LIBRARY_PATH as
"export LD_LIBRARY_PATH=/app/bds/parcels/ORACLE_INSTANT_CLIENT/instantclient_11_2:$LD_LIBRARY_PATH"