code: def format_num(num, unit='bytes'):
      
      if unit == 'bytes':
          extension = 'B'
      else:
          # if it's not bytes, it's bits
          extension = 'Bit'
      for dimension in (unit, 'K', 'M', 'G', 'T'):
          if num < 1024:
              if dimension == unit:
                  return '%3.1f %s' % (num, dimension)
              return '%3.1f %s%s' % (num, dimension, extension)
          num /= 1024
      return '%3.1f P%s' % (num, extension)
docs: Returns a human readable string of a byte-value.
      If 'num' is bits, set unit='bits'.