>>> class Student(object):
...   pass
...

>>> s = Student()
>>> s.name = 'Michael' # 动态给实例绑定一个属性
>>> print s.name
Michael

>>> def set_age(self, age): # 定义一个函数作为实例方法
...   self.age = age
...
>>> from types import MethodType
>>> s.set_age = MethodType(set_age, s, Student) # 给实例绑定一个方法
>>> s.set_age(25) # 调用实例方法
>>> s.age # 测试结果
25

>>> s2 = Student() # 创建新的实例
>>> s2.set_age(25) # 尝试调用方法
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
AttributeError: 'Student' object has no attribute 'set_age'

>>> def set_score(self, score):
...   self.score = score
...
>>> Student.set_score = MethodType(set_score, None, Student)

>>> s.set_score(100)
>>> s.score
100
>>> s2.set_score(99)
>>> s2.score
99

>>> class Student(object):
...   __slots__ = ('name', 'age') # 用tuple定义允许绑定的属性名称
...

>>> s = Student() # 创建新的实例
>>> s.name = 'Michael' # 绑定属性'name'
>>> s.age = 25 # 绑定属性'age'
>>> s.score = 99 # 绑定属性'score'
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
AttributeError: 'Student' object has no attribute 'score'

>>> class GraduateStudent(Student):
...   pass
...
>>> g = GraduateStudent()
>>> g.score = 9999
Try