鸭子类型

class duck():

  def walk(self):

    print('I walk like a duck')

  def swim(self):

    print('i swim like a duck')



class person():

  def walk(self):

    print('this one walk like a duck')

  def swim(self):

    print('this man swim like a duck')

def watch_duck(animal):

  animal.walk()

  animal.swim()

small_duck = duck()

watch_duck(small_duck)

output >>

I walk like a duck

i swim like a duck

duck_like_man = person()

watch_duck(duck_like_man)

output >>

this one walk like a duck

this man swim like a duck

class Lame_Foot_Duck():

  def swim(self):

    print('i am lame but i can swim')

lame_duck = Lame_Foot_Duck()

watch_duck(lame_duck)

output >>
AttributeError: Lame_Foot_Duck instance has no attribute 'walk'

看例子，传入def watch_duck函数的时候，就默认给了类的方法，如果没有这个方法，函数就会报错

在实际例子中，如果创建了一个类，它含有getitem()方法，那么它就可以看做是一个list类，这就是是所谓的鸭子类型