class Ctc(object):
	def __init__(self):
		self.name = "shun"
	def run(self):
		self.prea()
		self.a()
		self.b()
		self.c()
	def a(self):
		print("a")
	def b(self):
		print("b")
	def prea(self):
		print("Prea")

class TestInstance(Ctc):
	def __init__(self):
		self.name = "shun2"
	def a(self):
		print("aa")
	def b(self):
		print("bb")

class Another(TestInstance):
	def __init__(self):
		self.name = "another"
	def a(self):
		print("aa in Another")
	# def b(self):
	# 	print("bb in Another")
	def d(self):
		print("d in Another")

class Case(Another):
	def __init__(self):
		self.name = "shun3"
	def c(self):
		print("cc in case")
	# def b(self):
	# 	print("bbb")
	# def run(self):
	# 	print("run in case")

if __name__ == '__main__':
	test = Case()
	exit(test.run())

　　类的继承，会先找最底层的类是否有此函数，在找最接接近的类，直到最上层父类，就近原则