Python: changing methods and attributes at runtime

Question

I wish to create a class in Python that I can add and remove attributes and methods. How can I acomplish that?

Oh, and please don't ask why.

Answer 1

This example shows the differences between adding a method to a class and to an instance.

>>> class Dog(): ...     def __init__(self, name): ...             self.name = name ... >>> skip = Dog('Skip') >>> spot = Dog('Spot') >>> def talk(self): ...     print 'Hi, my name is ' + self.name ... >>> Dog.talk = talk # add method to class >>> skip.talk() Hi, my name is Skip >>> spot.talk() Hi, my name is Spot >>> del Dog.talk # remove method from class >>> skip.talk() # won't work anymore Traceback (most recent call last):   File "<stdin>", line 1, in <module> AttributeError: Dog instance has no attribute 'talk' >>> import types >>> f = types.MethodType(talk, skip, Dog) >>> skip.talk = f # add method to specific instance >>> skip.talk() Hi, my name is Skip >>> spot.talk() # won't work, since we only modified skip Traceback (most recent call last):   File "<stdin>", line 1, in <module> AttributeError: Dog instance has no attribute 'talk' 

Answer 2

I wish to create a class in Python that I can add and remove attributes and methods.

import types  class SpecialClass(object):     @classmethod     def removeVariable(cls, name):         return delattr(cls, name)      @classmethod     def addMethod(cls, func):         return setattr(cls, func.__name__, types.MethodType(func, cls))  def hello(self, n):     print n  instance = SpecialClass() SpecialClass.addMethod(hello)  >>> SpecialClass.hello(5) 5  >>> instance.hello(6) 6  >>> SpecialClass.removeVariable("hello")  >>> instance.hello(7) Traceback (most recent call last):   File "<stdin>", line 1, in <module> AttributeError: 'SpecialClass' object has no attribute 'hello'  >>> SpecialClass.hello(8) Traceback (most recent call last):   File "<stdin>", line 1, in <module> AttributeError: type object 'SpecialClass' has no attribute 'hello'