编写一个代表三角形的类，其中3条边为三角形的属性，并封装有求三角形的面积和周长的方法。分别利用3条边为3、4、5和7、8、9的两个三角形进行测试。

class Triangle:
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c
    
    def perimeter(self):
        return self.a + self.b + self.c
    
    def area(self):
        s = (self.a + self.b + self.c) / 2
        return (s * (s-self.a) * (s-self.b) * (s-self.c)) ** 0.5

triangle1 = Triangle(3, 4, 5)
print("Triangle 1 perimeter:", triangle1.perimeter())
print("Triangle 1 area:", triangle1.area())

triangle2 = Triangle(7, 8, 9)
print("Triangle 2 perimeter:", triangle2.perimeter())
print("Triangle 2 area:", triangle2.area())

输出结果：

Triangle 1 perimeter: 12
Triangle 1 area: 6.0
Triangle 2 perimeter: 24
Triangle 2 area: 26.832815729997478