定义多边形类 包含属性：点坐标数组，点数等信息，和三个函数分别为：赋值、求多变形周长函数、求多边形面积函数，用 main() 进行测试。

下面是定义多边形类的代码：

import math

class Polygon:
    def __init__(self):
        self.vertices = []
        self.n = 0

    def assign_vertices(self, vertices):
        self.vertices = vertices
        self.n = len(vertices)

    def perimeter(self):
        perimeter = 0
        for i in range(self.n):
            j = (i + 1) % self.n
            dx = self.vertices[i][0] - self.vertices[j][0]
            dy = self.vertices[i][1] - self.vertices[j][1]
            perimeter += math.sqrt(dx * dx + dy * dy)
        return perimeter

    def area(self):
        area = 0
        j = self.n - 1
        for i in range(self.n):
            area += (self.vertices[j][0] + self.vertices[i][0]) * (self.vertices[j][1] - self.vertices[i][1])
            j = i
        return abs(area / 2)

# 测试代码
if __name__ == '__main__':
    polygon = Polygon()
    polygon.assign_vertices([(0, 0), (0, 1), (1, 1), (1, 0)])
    print("多边形周长为：", polygon.perimeter())
    print("多边形面积为：", polygon.area())

测试输出：

多边形周长为： 4.0
多边形面积为： 1.0