Python类方法的使用

类方法也不属于某个对象，所以其第一个参数也不为self。但它属于某个类，所以其第一个参数一定是cls。

@classmethoddef static_func(cls, 参数列表):    pass

在使用时不需要指定第一个参数 cls，因为该函数有一个隐含的属性 __self__，它就是 cls 的值。

>>> class Student:     # 定义类
... highest_score = 0
... lowest_score = 100
... def __init__(self):     # 初始化函数
... self.name = ""
... @classmethod     # 类方法
... def get_highest_score(cls):
... print("cls = ", cls)
... return Student.highest_score
... def set_score(self, score):     # 普通成员函数
... if score > Student.highest_score:
... Student.highest_score = score
... if score < Student.lowest_score:
... Student.lowest_score = score
...     # 类定义结束
>>> student_a = Student()
>>> student_b = Student()
>>> student_c = Student()
>>> student_a.set_score(98)
>>> student_b.set_score(92)
>>> student_c.set_score(95)
>>> Student.get_highest_score()
('type = ', <class __main__.Student at 0x1047a7a78>)
98
>>> Student     # 类对象
<class __main__.Student at 0x1047a7a78>     # 函数的一个属性__self__就是类对象
>>> student_a.get_highest_score.__self__
<class __main__.Student at 0x1047a7a78>