code: def check_pidfile(pidfile, debug):
      
      # Check PID exists and see if the PID is running
      if os.path.isfile(pidfile):
          pidfile_handle = open(pidfile, 'r')
          # try and read the PID file. If no luck, remove it
          try:
              pid = int(pidfile_handle.read())
              pidfile_handle.close()
              if check_pid(pid, debug):
                  return True
          except:
              pass
  
          # PID is not active, remove the PID file
          os.unlink(pidfile)
  
      # Create a PID file, to ensure this is script is only run once (at a time)
      pid = str(os.getpid())
      open(pidfile, 'w').write(pid)
      return False
docs: Check that a process is not running more than once, using PIDFILE