python
class Circle:
def __init__(self):
self.radius = 0
def set_radius(self, radius):
if radius >= 0:
self.radius = radius
def get_radius(self):
return self.radius
def calculate_area(self):
return 3.14 * self.radius * self.radius
circle = Circle()
circle.set_radius(5)
python
class Animal:
def __init__(self, name):
self.name = name
def speak(self):
pass
class Dog(Animal):
def speak(self):
class Cat(Animal):
def speak(self):
python
class Shape:
def calculate_area(self):
pass
class Circle(Shape):
def __init__(self, radius):
self.radius = radius
def calculate_area(self):
return 3.14 * self.radius * self.radius
class Rectangle(Shape):
def __init__(self, width, height):
self.width = width
self.height = height
def calculate_area(self):
return self.width * self.height
shapes = [Circle(5), Rectangle(3, 4)]
for shape in shapes:
