求正方形的面积和周长

 1 class Square:
 2     def __init__(self,length):
 3         self.length = length
 4 
 5     def perimeter(self):
 6         return 4*self.length
 7 
 8     def area(self):
 9         return self.length*self.length
10 
11 square = Square(3)
12 print(square.perimeter())
13 print(square.area())