code: def _len_list(obj):
      '''Length of list (estimate).
      '''
      n = len(obj)
       # estimate over-allocation
      if n > 8:
         n += 6 + (n >> 3)
      elif n:
         n += 4
      return f _len_list(obj):
      '''Length of list (estimate).
      '''
      n = len(obj)
       # estimate over-allocation
      if n > 8:
         n += 6 + (n >> 3)
      elif n:
         n += 4
      return n
docs: Length of list (estimate).