一憔杨、sort呕臂，sorted函數(shù)介紹：
Sort函數(shù)是list列表中的函數(shù)摄狱，而sorted可以對(duì)list或者iterator進(jìn)行排序胖腾。
下面我們使用help來(lái)查看他們的用法及功能：
sort：
>>> help(list.sort)
Help on method_descriptor:
sort(...)
L.sort(key=None, reverse=False) -> None -- stable sort *IN PLACE*
sorted：
Python3.x:
>>> help(sorted)
Help on built-in function sorted in module builtins:
sorted(iterable, /, *, key=None, reverse=False)
Return a new list containing all items from the iterable in ascending order.
A custom key function can be supplied to customize the sort order, and the
reverse flag can be set to request the result in descending order.
Python2.x:
>>> help(sorted)
Help on built-in function sorted in module __builtin__:
sorted(...)
sorted(iterable, cmp=None, key=None, reverse=False) --> new sorted list
Python3.x和Python2.x的sorted函數(shù)有點(diǎn)不太一樣，少了cmp參數(shù)幕袱。
二暴备、sort和sorted的比較：
用sort函數(shù)對(duì)列表排序時(shí)會(huì)影響列表本身，而sorted不會(huì)们豌。
舉例：
>>> a = [1,2,1,4,3,5]
>>> a.sort()
>>> a
[1, 1, 2, 3, 4, 5]
>>> a = [1,2,1,4,3,5]
>>> sorted(a)
[1, 1, 2, 3, 4, 5]
>>> a
[1, 2, 1, 4, 3, 5]
Python2.x的sorted函數(shù)：sorted(iterable涯捻，cmp，key望迎，reverse）
參數(shù)：
- iterable可以是list或者iterator障癌；
- cmp是帶兩個(gè)參數(shù)的比較函數(shù)；
- key 是帶一個(gè)參數(shù)的函數(shù)辩尊；
- reverse為False或者True涛浙；
舉例說(shuō)明:
（1）用cmp函數(shù)排序:
>>> list1 = [('david', 90), ('mary',90), ('sara',80),('lily',95)]
>>> sorted(list1,cmp = lambda x,y: cmp(x[0],y[0]))
[('david', 90), ('lily', 95), ('mary', 90), ('sara', 80)]
>>> sorted(list1,cmp = lambda x,y: cmp(x[1],y[1]))
[('sara', 80), ('david', 90), ('mary', 90), ('lily', 95)]
（2）用key函數(shù)排序:
>>> list1 = [('david', 90), ('mary',90), ('sara',80),('lily',95)]
>>> sorted(list1,key = lambda list1: list1[0])
[('david', 90), ('lily', 95), ('mary', 90), ('sara', 80)]
>>> sorted(list1,key = lambda list1: list1[1])
[('sara', 80), ('david', 90), ('mary', 90), ('lily', 95)]
（3）用reverse排序:
>>> sorted(list1,reverse = True)
[('sara', 80), ('mary', 90), ('lily', 95), ('david', 90)]
（4）用operator.itemgetter函數(shù)排序:
>>> from operator import itemgetter
>>> sorted(list1, key=itemgetter(1))
[('sara', 80), ('david', 90), ('mary', 90), ('lily', 95)]
>>> sorted(list1, key=itemgetter(0))
[('david', 90), ('lily', 95), ('mary', 90), ('sara', 80)]
介紹operator.itemgetter函數(shù):
>>> import operator
>>> a = [1,2,3]
>>> b = operator.itemgetter(0)
>>> b(a)
operator.itemgetter函數(shù)獲取的不是值，而是定義了一個(gè)函數(shù)摄欲。
（5）多級(jí)排序:
>>> sorted(list1, key=itemgetter(0,1))
[('david', 90), ('lily', 95), ('mary', 90), ('sara', 80)]
