title: Copying file through python
body: <p>I'm copying a single large archive file through python by reading and writing source and destination file (in byte mode)through OPEN function because I need to display a progress bar.</p>
  
  <p>Now how much buffer should I read and write in each loop so that copy is fast enough and doesn't feel slow compared to copying through OS. Is there any way to calculate this optimum buffer amount keeping in mind network speed or any other factor?</p>