Python的attrgetter()

# -*- coding: utf-8 -*-# 在排序时, 可以用lambda表达式将对象map成keys# 亦可以使用operator包中的attrgetter和itemgetter函数以提高效率# 参考 http://wiki.python.org/moin/HowTo/Sorting# 考虑 Student 对象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))# 建立一组Student对象students = [    Student('jane', 'B', 12),    Student('john', 'A', 12),    Student('dave', 'B', 10),]from operator import itemgetter, attrgetter# 对students按照年龄排序print sorted(students, key=attrgetter('age'))# 其等价于print sorted(students, key=lambda o: o.age)# 输出: >>> [('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]# 亦可以按多个key排序, 先按age再按grade排序print sorted(students, key=attrgetter('age', 'grade'))# 输出: >>> [('dave', 'B', 10), ('john', 'A', 12), ('jane', 'B', 12)]