# 有时候你编写了一堆类当数据结构用,但是懒得写一堆init函数,这时候可以将初始化数据结构的init函数归纳到一个公共基类中

class Structure:
    _fields = []
    def __init__(self, *args, **kwargs):
        if len(args) > len(self._fields):
            raise TypeError("Expect {} arguments, but only {}".format(len(self._fields), len(args)))

        # 处理顺序输入的参数
        for name, value in zip(self._fields, args):
            setattr(self, name, value)

        # 处理关键字参数
        for name in args[len(self._fields):]:
            setattr(self, name, kwargs.pop(name))

        # 处理多余的关键字参数
        if kwargs:
            raise TypeError("Invalid arguments {}".format(",".join(kwargs)))


class lazy:
    def __init__(self, func):
        self.func = func

    def __get__(self, instance, cls):
        if instance is None:
            return self
        else:
            value = self.func(instance)
            setattr(instance, self.func.__name__, value)
            return value

# 这时候我们会发现你只需要指定参数就行了,异常的好使
import math
if __name__ == '__main__':

    class Stock(Structure):
        _fields = ["name", "shares", "price"]
        __slots__ = _fields

    class Points(Structure):
        _fields = ["x", "y"]
        __slots__ = _fields


    class Circle(Structure):
        _fields = ["radius"]
        __slots__ = _fields
        @lazy
        def area(self):
            return math.pi * self.radius ** 2

    s = Stock('ACME', 50, 91.1)
    p = Points(2,3)
    c = Circle(4.5)
    print(c.area)
    print(c.area)