1. reversed
class reversed(object)
| reversed(sequence) -> reverse iterator over values of the sequence
|
| Return a reverse iterator
|
| Methods defined here:
|
| __getattribute__(...)
| x.__getattribute__('name') <==> x.name
|
| __iter__(...)
| x.__iter__() <==> iter(x)
|
| __length_hint__(...)
| Private method returning an estimate of len(list(it)).
|
| next(...)
| x.next() -> the next value, or raise StopIteration
|
| ----------------------------------------------------------------------
| Data and other attributes defined here:
|
| __new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
处理的对象是可迭代对象，返回值是一个迭代器，所以可以处理string list 等，如下：
In [54]: reversed([1,2,3])
Out[54]: <listreverseiterator at 0x7f835810c190>
In [55]: reversed('123')
Out[55]: <reversed at 0x7f835810c2d0>
In [56]: type(reversed('123'))
Out[56]: reversed
In [57]: for i in reversed('123'):
....: print i
....:
3
2
1
PS： list内置__reversed__()方法实现的功能和此类似，使用方法见2
2. reverse
reverse是list内置的一个方法，所以只能对list使用，如下：
In [62]: l = [1, 2, 3]
In [63]: l.reverse()
In [64]: l
Out[64]: [3, 2, 1]
__reversed__()
In [65]: l.__reversed__()
Out[65]: <listreverseiterator at 0x7f835810ca90>
In [66]: for i in l.__reversed__():
....: print i
....:
1
2
3
3. 切片
最简单的一种方法了，可以对string和list使用
In [73]: s
Out[73]: 'i am a student.'
In [74]: s[::-1]
Out[74]: '.tneduts a ma i'
In [75]: l
Out[75]: [3, 2, 1]
In [76]: l[::-1]
Out[76]: [1, 2, 3]