Python 中有非常方便高效的排序函数，下面主要介绍如何sort/sorted对list，dict进行排序。
1. 用list.sort /sorted 对list of tuples中第二个值进行排序
>>> import operator >>> a=[(‘a‘,3),(‘b‘,2),(‘c‘,1)] >>> import operator >>> l=[(‘a‘,3),(‘b‘,2),(‘c‘,1)] >>> l.sort(key=operator.itemgetter(1)) >>> l [(‘c‘, 1), (‘b‘, 2), (‘a‘, 3)] >>> sorted(l, key=operator.itemgetter(1)) [(‘c‘, 1), (‘b‘, 2), (‘a‘, 3)] >>> sorted(l, key=operator.itemgetter(0)) [(‘a‘, 3), (‘b‘, 2), (‘c‘, 1)]
list.sort 和sorted 的区别：sort是list序列的一个方法，而sorted是内建函数
list.sort: 没有返回值，而且 sort作为序列的内部函数，调用完后会对调用的序列进行排序
sorted：函数不改变参数，并返回排好序的序列副本
在python开发文档中对sort和sorted都有详细介绍，也可以调用help函数来查看两者的区别
>>> help(list.sort)
Help on method_descriptor:
sort(...)
L.sort(key=None, reverse=False) -> None -- stable sort *IN PLACE*
>>> 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.
2. 除了用operator之外我们也可以用lambda
>>> l.sort(key=lambda x:x[1]) >>> l [(‘c‘, 1), (‘b‘, 2), (‘a‘, 3)]
3. 用sorted来对ditionary进行排序
>>> l = {‘a‘: 3,"b": 2,"c": 1}
>>> sl_key = sorted(l.items()) #Sort by key
>>> sl_key
[(‘a‘, 3), (‘b‘, 2), (‘c‘, 1)]
>>> sl_value = sorted(l.items(),key=lambda x:x[1]) #Sort by value
>>> sl_value
[(‘c‘, 1), (‘b‘, 2), (‘a‘, 3)]
>>> sl_value = sorted(l.items(),key=lambda x:x[1],
reverse=True) #Sort by value Backwards
>>> sl_value
[(‘a‘, 3), (‘b‘, 2), (‘c‘, 1)]
>>> sl_value = sorted(l.items(),key=lambda x:(x[1],x[0]),
reverse=True) #Sort by value then by Key
>>> sl_value
[(‘a‘, 3), (‘b‘, 2), (‘c‘, 1)]
