Python合并多个Excel文件

网上抄的一段代码，可以把多个文件合并起来。

import pandas as pd
file1='jan.xls'
file2='feb.xls'
file3='mar.xls'
file4='apr.xls'
file5='may.xls'
file6='jun.xls'
file7='jul.xls'
file8='aug.xls'
file9='sep.xls'
file=[file1,file2,file3,file4,file5,file6,file7,file8,file9]
li=[]
for i in file:
  li.append(pd.read_excel(i))
writer = pd.ExcelWriter('output.xls')
pd.concat(li).to_excel(writer,'Sheet1',index=False)
writer.save()