本文是阅读python文档笔记，地址：https://docs.python.org/3/howto/sorting.html
内容：
- Python中有内置方法list.sort()，这个方式是会改变原来的list，也有内置函数sorted()，这个函数会返回一个新的list。文章主要讲各种方式排序数据in Python。
- list.sort()方法仅仅只为list定义，而sorted()函数可以接受任何可以迭代的对象。
>>>sorted({1: 'D', 2: 'B', 3: 'B', 4: 'E', 5: 'A'})
>>>[1, 2, 3, 4, 5]
- list.sort()和sorted()都有key参数，指定排序规则。这个参数接收的应该是一个函数，如下lambda
>>> sorted("This is a test string from Andrew".split(), key=str.lower)
>>> ['a', 'Andrew', 'from', 'is', 'string', 'test', 'This']
>>> student_tuples = [
('john', 'A', 15),
('jane', 'B', 12),
('dave', 'B', 10),
]
>>> sorted(student_tuples, key=lambda student: student[2]) # sort by age
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
>>> class Student:
def __init__(self, name, grade, age):
self.name = name
self.grade = grade
self.age = age
def __repr__(self):
return repr((self.name, self.grade, self.age))
>>> student_objects = [
Student('john', 'A', 15),
Student('jane', 'B', 12),
Student('dave', 'B', 10),
]
>>> sorted(student_objects, key=lambda student: student.age) # sort by age
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
- Operator Module Functions：python提供了几个非常方便的函数来获取key参数—itemgetter、attrgetter、 methodcaller
>>> from operator import itemgetter, attrgetter
>>> sorted(student_tuples, key=itemgetter(2))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
>>> sorted(student_objects, key=attrgetter('age'))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
>>> sorted(student_tuples, key=itemgetter(1,2))
[('john', 'A', 15), ('dave', 'B', 10), ('jane', 'B', 12)]
>>> sorted(student_objects, key=attrgetter('grade', 'age'))
[('john', 'A', 15), ('dave', 'B', 10), ('jane', 'B', 12)]
- list.sort()和sorted()还有一个reserve参数，它是一个boolean值
>>> sorted(student_tuples, key=itemgetter(2), reverse=True)
[('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]
>>> sorted(student_objects, key=attrgetter('age'), reverse=True)
[('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]
