hard q30: define 3 classes

q30/shapes.py

@@ -0,0 +1,14 @@
+class Shape:
+    def area(self):
+        return 0
+
+class Circle(Shape):
+    def area(self):
+        return 3.14 * r * r
+
+class Square(Shape):
+    def area(self):
+        return side * side
+
+if __name__ == '__main__':
+