python如何实现反向迭代

#!/usr/bin/python3 l = [1, 2, 3, 4, 5, 6]l.reverse()for i in l:  print(i)   # 出现问题，改变了原列表，不可取

#!/usr/bin/python3 l = [1, 2, 3, 4, 5, 6]for i in l[::-1]:  print(i)   # 得到了和原列表等大的列表，某种程度上很浪费

#!/usr/bin/python3 l = [1, 2, 3, 4, 5, 6] for i in reversed(l):  print(i)

#!/usr/bin/python3  class FloatRange(object):  def __init__(self, start, end, step):    self.dot = self.__get_dot_num(step)    # 有多少个小数点就乘以10的多少次幂，因为浮点数运算不准确，换算成整形数进行计算    self.start = start*pow(10, self.dot)    self.end = end*pow(10, self.dot)    self.step = step*pow(10, self.dot)       def __get_dot_num(self, step):    # 计算step有多少个小数点    if isinstance(step, int):      return step    else:      # 通过round实现计算有多少位小数，首创      for dot in range(len(str(step))+1):        if step == round(step, dot):          return dot   def __iter__(self):    # 正向迭代    while self.start <= self.end:      yield self.start/pow(10, self.dot)      self.start += self.step   def __reversed__(self):    # 反向迭代    while self.end >= self.start:      yield self.end/pow(10,self.dot)      self.end -= self.step if __name__ == '__main__':     float_num_1 = FloatRange(2, 5, 0.1)  float_num_2 = FloatRange(2, 5, 0.1)     # 正向迭代  for i in float_num_1:    print(i)       print('_'*60)     # 反向迭代  for x in reversed(float_num_2):    print(x)