Dumping Second column with python

import sys
import xlrd

filename = sys.argv[1]

sheet = xlrd.open_workbook(filename).sheet_by_index(0)
#sheet = book.sheet_by_index(0)
csv_filename = filename.replace(".xlsx", ".csv")

csv_fh = open(csv_filename, 'w')

for rownum in range(2, sheet.nrows):
    if isinstance(sheet.cell(rownum, 1).value, float):
        print(int(sheet.cell_value(rownum,1)))
        csv_fh.write(str(int(sheet.cell_value(rownum,1))) + '\n')