cx_oracle: How do you pass variable value in placeholder with OFFSET clause in python

[Srikanta2020]

Hi ,
Whenever trying run below code , i am getting error " cur.execute("select * from nm_src_lkup ORDER BY NM_SRC_CD OFFSET :row_count ROWS") cx_Oracle.DatabaseError: ORA-01008: not all variables bound" . i am passing rowcount variable value in OFFSET cluase with select query .but it's not working .Please help me out

from time import sleep
import sys
import cx_Oracle
import csv
IDLE_INTERVAL_IN_SECONDS = 100
dsn_tns = cx_Oracle.makedsn('xxxx.com', '1521', service_name='ppxxx.com') 
conn = cx_Oracle.connect('MDBSE','mdbB5se', dsn=dsn_tns)
cur = conn.cursor()
row_count = 0
while True:
    cur.execute("select * from nm_src_lkup ORDER BY NM_SRC_CD OFFSET :row_count ROWS")
    row_count = cur.rowcount
    if row_count > 0:
        file = open("skp1.csv","w")
        output = csv.writer(file , dialect='excel')
        for row_data in cur:
        output.writerow(row_data)
    sleep(IDLE_INTERVAL_IN_SECONDS)