title: write text file without deleting older saves with python
body: <p>I'm somewhat new to python and I want to create a new txt file <strong>without replacing</strong> the old file</p>
  
  <p>I try this to create a new file:</p>
  
  <pre><code>def savebill():
  
      lineadd=" -------------------------------------------\n" 
      print (lineadd)
      bill=open('bill.txt','w')
      bill.write(lineadd)
      bill.close()
  </code></pre>
  
  <p>When I Want to save <strong>a new</strong> bill the old file  it will be replaced,I need to <strong>keep a copy of the old saves</strong>.</p>