python中可迭代对象的排序

1、字符串排序

>>> a = "349217"
>>> b = sorted(a)
>>> b
['1', '2', '3', '4', '7', '9']
>>> type(b)   ## 返回类型为列表
<class 'list'>
>>> c = sorted(a,reverse = True)   ## 逆向排序
>>> c
['9', '7', '4', '3', '2', '1']
>>> "".join(b)   ## 拼接字符串
'123479'
>>> "".join(c)
'974321'
>>> a.sort()    ## 字符串不能够就地排序
Traceback (most recent call last):
  File "<pyshell#345>", line 1, in <module>
    a.sort()
AttributeError: 'str' object has no attribute 'sort'
>>> 

2、列表排序

>>> a = [3,9,5,2,7]
>>> b = sorted(a)  ## 使用sorted排序，原变量不变
>>> b
[2, 3, 5, 7, 9]
>>> c = sorted(a,reverse = True)  ## 逆向排序
>>> c
[9, 7, 5, 3, 2]
>>> a
[3, 9, 5, 2, 7]
>>> a.sort()   ## 就地排序
>>> a
[2, 3, 5, 7, 9]
>>> a.sort(reverse = True)  ## 就地逆向排序
>>> a
[9, 7, 5, 3, 2]

3、元组排序

>>> a = (8,2,3,9,5)
>>> b = sorted(a)   ## sorted排序，原变量不变
>>> b
[2, 3, 5, 8, 9]
>>> c = sorted(a,reverse = True)  ## 逆向排序
>>> c
[9, 8, 5, 3, 2]
>>> a
(8, 2, 3, 9, 5)
>>> a.sort()   ## 元组不能就地排序
Traceback (most recent call last):
  File "<pyshell#374>", line 1, in <module>
    a.sort()
AttributeError: 'tuple' object has no attribute 'sort'