title: Append new sheet with data in existing excel file
body: <p>Reading files (1234-P2P.xlsx, 1234-T2T)  and creating excel file with name 1234.xlsx and sheets inside the file like 'P2P', 'T2T' and so on .
  First file read and write is done,When writing 2nd file it overrides first sheet.Need to append new sheet in same file keeping previous sheets. </p>
  
  <pre><code>def Userwise(d,filedata):
   splitWord=[]
   splitWord=d.split('-')
  
   df1=filedata.parse('sheet1')
  
   writer=ExcelWriter(splitWord[0]+'.xlsx')
   df1.to_excel(writer,splitWord[1],header=True,index=False)
   print(df1)
   writer.save()
  
  
  path = 'C:\\DE\\pythonFile\\pandas\\Userwise'
  d=[]
  
  for f in os.listdir(path):
   filedata=pd.ExcelFile('C:\\DE\\pythonFile\\pandas\\Userwise\\'+f)
   d=f[:-5]
   Userwise(d,filedata)
  </code></pre>
  
  <p>1 file with name '1234.xlsx' with sheets inside like 'P2P', 'T2T' with data</p>