如何进行反向迭代以及如何实现反向迭代？

需求：
实现一个连续浮点数发生器FloatRange和（range类似），根据给定的范围（start,end)和步进值（step)产生一些列连续浮点数，如迭代FloatRange(3.0,4.0,0.2)可产生序列：
正向：3.0-->3.2-->3.4-->3.6-->3.8-->4.0
反向：4.0-->3.8-->3.6-->3.4-->3.2-->3.0
思路：
实现反向迭代协议的__reversed__方法，它返回一个反向迭代器。
代码：

class FloatRange:
    def __init__(self,start,end,step=0.1):
        self.start = start
        self.end = end
        self.step = step

    def __iter__(self):
        t = self.start
        while t <= self.end:
            yield t
            t += self.step

    def __reversed__(self):
        t = self.end
        while t >= self.start:
            yield t
            t -= self.step

if __name__=='__main__':

    for x in reversed(FloatRange(1.0,4.0,0.5)):
        print(x)

====================================================

from decimal import Decimal
class FloatRange:
    def __init__(self,a,b,step):
        self.a = Decimal(str(a))  # 此处是为了消除10进制和2进制浮点数转换中的误差
        self.b = Decimal(str(b))
        self.step = Decimal(str(step))

    def __iter__(self):
        t = self.a
        while t <= self.b:
            yield float(t)  # 将字符串类型转换成浮点数的类型
            t += self.step

    def __reversed__(self):
        t = self.b
        while t >= self.a:
            yield float(t)
            t -= self.step

fr = FloatRange(3.0,4.0,0.2)

for x in fr:
    print(x)

print('-' * 20)

for x in reversed(fr):
    print(x)

=========================================================

>>> l = [1,2,3,4,5]

>>> l.reverse()

>>> l
[5, 4, 3, 2, 1]

>>> l[::-1]
[1, 2, 3, 4, 5]

>>> l = [1,2,3,4,5]

>>> reversed(l)
<list_reverseiterator at 0x7fafb4cccc50>

>>> iter(l)
<list_iterator at 0x7fafaf4c3e48>

>>> for x in reversed(l):
...     print(x)
... 
5
4
3
2
1

>>> d = {}

>>> reversed(d)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-10-b13b185f39f7> in <module>
----> 1 reversed(d)

TypeError: 'dict' object is not reversible

>>> s = 'abc'

>>> reversed(s)
<reversed at 0x7fafaf700cc0>

>>> from decimal import Decimal

>>> Decimal('0.2')
Decimal('0.2')

>>> from functools import reduce

>>> reduce(Decimal.__add__,[Decimal('0.2')] * 5)
Decimal('1.0')

>>> reduce(Decimal.__add__,[Decimal('0.2')] * 30)
Decimal('6.0')

>>> Decimal(0.2)
Decimal('0.200000000000000011102230246251565404236316680908203125')

>>> Decimal('0.2') > Decimal('0.1')
True

>>>