【笔记】反向迭代

实现一个连续浮点数发生器FloatRange，产生一些连续浮点数。

实现反向迭代协议的__reversed__方法，它返回一个迭代器。

 1 class FloatRange:
 2     def __init__(self,start,end,step = 0.1):
 3         self.start = start
 4         self.end = end
 5         self.step = step
 6
 7     def __iter__(self):
 8         t = self.start
 9         while t <= self.end:
10             yield t
11             t += self.step
12
13     def __reversed__(self):
14         t = self.end
15         while t >= self.start:
16             yield t
17             t -= self.step
18
19 if __name__ == "__main__":
20
21     for x in FloatRange(1.0,4.0,0.5):
22         print x
23
24     for x in reversed(FloatRange(1.0,4.0,0.5)):
25         print x
26