创建Circle和Square子类并且重写area方法

main.py

@@ -1,3 +1,13 @@
 class Shape:
     def area(self):
         return 0
+class Circle(Shape):
+    def __init__(self,r):
+        self.r = r
+    def area(self):
+        return (3.14*self.r*self.r)
+class Square(Shape):
+    def __init__(self,side):
+        self.side = side
+    def area(self):
+        return (self.side*self.side)