python 面向对象开发及基本特征

import math
class Vectors:
    def __init__(self):
        self.x1 = 0
        self.x2 = 0
        self.y1 = 0
        self.y2 = 0
        self.x = self.x2 - self.x1
        self.y = self.y2 - self.y1
    def add(self):
        self.x1 = int(input("input x1 "))
        self.y1 = int(input("input y1 "))
        self.x2 = int(input("input x2 "))
        self.y2 = int(input("input y2 "))
    def out(self):
        print(self.x, self.y)
    def plus(self, a, b):
        self.x = a.x + b.x
        self.y = a.y + b.y
    def sub(self, a, b):
        self.x = a.x - b.x
        self.y = a.y - b.y
    def pointmuti(self, a, b):
        return (a.x * b.x + a.y * b.y)
    def angle(self, a, b):
        a1 = (a.x * a.x + a.y * a.y) ** 0.5
        b1 = (b.x * b.x + b.y * b.y) ** 0.5
        ab = a.x * b.x + a.y * b.y
        return ab // (a1 * b1)
v = Vectors()
a = Vectors()
b = Vectors()
a.add()
b.add()
a.out()
b.out()
v.plus(a, b)
v.out()
v.sub(a, b)
print(v.pointmuti(a, b))
print(math.acos(v.angle(a, b)))

import math
class Triangle:
    def __init__(self):
        a = 0
        b = 0
        c = 0
    def add(self):
        self.a = int(input("输入第1条边的长度："))
        self.b = int(input("输入第2条边的长度："))
        self.c = int(input("输入第3条边的长度："))
        while (self.a + self.b <= self.c):
            print("不符合三角边的规定，重新输入！")
            self.a = int(input("输入第1条边的长度："))
            self.b = int(input("输入第2条边的长度："))
            self.c = int(input("输入第3条边的长度："))
    def out(self):
        print(self.a, self.b, self.c)
    def length(self):
        return self.a+self.b+self.c
    def area(self):
        p=self.length()/2
        print(math.sqrt(p*(p-self.a)*(p-self.b)*(p-self.c)))
t = Triangle()
t.add()
t.out()
t.area()