python（Class8）

通过实例方法名字的字符串调用方法

内置函数getattr
标准库operator下的methodcaller函数

class Circle(object):
    def __init__(self, r):
        self._r = r

    def area(self):
        return self._r ** 2 * 3.14


class Rectangle(object):
    def __init__(self, w, h):
        self._w = w
        self._h = h

    def get_area(self):
        return self._w * self._h


class Triangle(object):
    def __init__(self, a, b, c):
        self._a = a
        self._b = b
        self._c = c

    def getArea(self):
        a, b, c = self._a, self._b, self._c
        p = (a+b+c)/2
        return (p*(p-a)*(p-b)*(p-c)) ** 0.5


def getarea(shape):
    for name in ('area', 'get_area', 'getArea'):
        f = getattr(shape, name, None)
        if f:
            return f()

shape1 = Circle(2)
shape2 = Rectangle(6, 4)
shape3 = Triangle(3, 4, 5)

shapes = [shape1, shape2, shape3]

print(list(map(getarea, shapes)))