继承

import random as r

class Fish:
	def __init__(self):
		self.x = r.randint(0,10)
		self.y = r.randint(0,10)

	def move(self):
		self.x -= 1
		print("My position is :",self.x,self.y)


class Goldfish(Fish):
	pass


class Salmon(Fish):
	"""docstring for Salmon"""
	#def __init__()
	def __init__(self):
		super().__init__()
		self.hungry = True
	def eat(self):
		if self.hungry:
			print("Salmon is full")
			self.hungry = False
		else:
			print("salmon eats too much")
	
# class Salmon(Fish):
# 	"""docstring for Salmon"""
# 	#def __init__()
# 	def __init__(self):
# 		super(Salmon,self).__init__()
# 		self.hungry = True
# 	def eat(self):
# 		if self.hungry:
# 			print("Salmon is full")
# 			self.hungry = False
# 		else:
# 			print("salmon eats too much")


class Shark(Fish):

	def __init__(self):
		Fish.__init__(self)     #self是子类的对象Fish.__init__(Shark)
		self.hungry = True
	def eat(self):
		if self.hungry:
			print("shark is full")
			self.hungry = False
		else:
			print("shark eats too much")

salmon = Salmon()
salmon.move()
salmon.eat()

shark = Shark()
shark.move()
shark.eat()

>>> class BB:
...     def printBB():
...         print('not binded')
... 
>>> BB.printBB()
not binded
>>> bb = BB()
>>> bb.printBB()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: printBB() takes 0 positional arguments but 1 was given

>>> class BB:
...     def printBB(self):
...         print('binded')
... 
>>> bb = BB()
>>> bb.printBB()
binded