python 实现在Excel末尾增加新行

import os
import xlrd
import xlwt
from xlutils.copy import copy

def excelwrite(L=None):
	if L is None:
		L = []
	print(L)
	filename = r'wldata.xls'
	workbook = xlrd.open_workbook(filename, formatting_info=True)
	sheet = workbook.sheet_by_index(0)
	rowNum = sheet.nrows
	colNum = sheet.ncols
	newbook = copy(workbook)
	newsheet = newbook.get_sheet(0)
	# 在末尾增加新行
	str = 'hehe'
	newsheet.write(rowNum, 0, str)
	# 覆盖保存
	newbook.save(filename)