# class Cls:
#     def __init__(self, name):
#         self.name = name
#         self.student = []
#     def __len__(self):
#         return len(self.student)
# py22 = Cls('py22')
# py22.student.append('小明')
# py22.student.append('xiaohong')
# py22.student.append('小黑')
# print(len(py22))
