Lex Li

You should read https://github.com/etingof/pysnmp/issues/429 for details on which version of PySNMP you should use and why. The technical support also moved away from here for long.

"1.3.6.2.1.33.1.3.3.1.3" is invalid. 1) It must start with "1.3.6.1.2.1", not "1.3.6.2.1" (I think you had a typo here). 2) "1.3.6.1.2.1.33.1.3.3" (upsInputTable) is a table, so "1.3.6.1.2.1.33.1.3.3.1.3" won't work as you didn't follow the SNMP table OID pattern to provide the index. Since you are new to SNMP, time to finish a book like Essential SNMP and get started.