Cx_Oracle using 'TO_DATE' in python

I want to call Oracle function within Python using cx_oracle

Oracle function:

function SetMessageInfo(  plogid                     number,
                          pmess_oper_status          number,
                          pmess_reason_code          number,
                          pmess_counter_measure_code number,
                          poper_trans_date           date) return number;

Python:

plogid = 215
pmess_oper_status = None
pmess_reason_code = 1
pmess_counter_measure_code = 1
now = datetime.datetime.now()

try:    
                result_end = curOracle.callfunc('PKG_IMPORT.setmessageinfo', int, [plogid, pmess_oper_status, pmess_reason_code, pmess_counter_measure_code, now.strftime('%Y-%m-%d %H:%M')])
            except Exception as err:
                print('Can not execute setmessageinfo',err)
            else:
                print('Succesfully executed setmessageinfo')

and I get cx_Oracle.DatabaseError: ORA-06502: PL/SQL: numeric or value error: character to number conversion error.

UPD: Solved. When using cx_Oracle call_func need to pass as parameter all variables, i.e. even those which are not mandatory by PL/SQL function.