def format_bytes(bytes, decimals=2):
  if bytes is None: return "Incalculable"
  if bytes < 1: return "0 B"

  i = 0
  while bytes >= 1024:
    bytes /= 1024
    i += 1

  units = ["B", "KB", "MB", "GB", "TB", "PB"]
  dm = decimals if bytes % 1 != 0 else 0
  return f"{bytes:.{dm}f} {units[i]}"