title: Python seek on remote file using HTTP
body: <p>How do I seek to a particular position on a remote (HTTP) file so I can download only that part?</p>
  
  <p>Lets say the bytes on a remote file were: 1234567890</p>
  
  <p>I wanna seek to 4 and download 3 bytes from there so I would have: 456</p>
  
  <p>and also, how do I check if a remote file exists?
  I tried, os.path.isfile() but it returns False when I'm passing a remote file url.</p>