列表元素是对象，对这样的列表排序方法

• 添加类方法使用lt

class MyClass:
    def __index__(self):
        self.value = 0

    def __lt__(self, other):
        return self.value < other.value

my1 = MyClass()
my1.value = 20

my2 = MyClass()
my2.value = 10

my3 = MyClass()
my3.value = 30

a = [my1,my2,my3]


a.sort()
print(a[0].value)
print(a[1].value)
print(a[2].value)

image.png

• 添加类方法使用gt

class MyClass:
    def __index__(self):
        self.value = 0
    '''
        def __lt__(self, other):
        return self.value < other.value
    '''
    def __gt__(self, other):
        return self.value > other.value


my1 = MyClass()
my1.value = 20

my2 = MyClass()
my2.value = 10

my3 = MyClass()
my3.value = 30

a = [my1,my2,my3]


a.sort()
print(a[0].value)
print(a[1].value)
print(a[2].value)

image.png

• 使用operator类

class MyClass:
    def __index__(self):
        self.value = 0

my1 = MyClass()
my1.value = 20

my2 = MyClass()
my2.value = 10

my3 = MyClass()
my3.value = 30

import operator   #导入operator

a = [my1,my2,my3]

a.sort(key=operator.attrgetter('value'))
b = sorted(a,key=operator.attrgetter('value'))


print(a[0].value)
print(a[1].value)
print(a[2].value)

print('b:',b[0].value)

image.png

列表元素是对象，对这样的列表如何进行倒序排列

• 添加参数reverse = True

class MyClass:
    def __index__(self):
        self.value = 0

my1 = MyClass()
my1.value = 20

my2 = MyClass()
my2.value = 10

my3 = MyClass()
my3.value = 30

import operator

a = [my1,my2,my3]

a.sort(key=operator.attrgetter('value'),reverse=True)
b = sorted(a,key=operator.attrgetter('value'))


print(a[0].value)
print(a[1].value)
print(a[2].value)

image.png

• 将lt,gt的符号改成相反的即可

    def __lt__(self, other):
        return self.value > other.value

    def __gt__(self, other):
        return self.value < other.value

总结

1.为类添加gt & lt 的方法，可以让类的实例支持sort,sorted函数
2.通过改变gt & lt方法的返回值，或者设置一下sort,sorted函数的reverse参数，就可以让列表倒序排列