Python-openpyxl和文件IO问题

import openpyxl as xl

peoples = ''
wb = xl.load_workbook('six.xlsx')
sheet = wb['Sheet1']

for row in range(2, sheet.max_row + 1):
    cell = sheet.cell(row, 2)
    peoples = cell.value
    print(peoples)

DATA = open('DATA.txt', 'w')
DATA.write(peoples)
DATA.close()

这段代码运行报错：

怎么解决这个问题？？？
求解答

翻译一下就知道了
write（）必须是字符创，不能是""和None