try:
    age = int (input("Age: "))
    income = 20000
    risk = income / age
    print(age)
except ZeroDivisionError:
    print(‘Age cannot be 0. ‘)
except ValueError:
    print(‘Invalid value‘)

class Point:
    def move(self):
        print(‘move‘)

    def draw(self):
        print(‘draw‘)

class Mammal:
    def walk(self):
        print(‘walk‘)
class Dog:
    pass#不定义一个空类


class Cat:
    pass