小编Spo*_*ock的帖子

我知道在Python中可以在运行时向类添加一个方法:

class Test:
    def __init__(self):
        self.a=5

test=Test()

import types
def foo(self):
    print self.a
test.foo = types.MethodType(foo, test)
test.foo() #prints 5

而且我也知道可以覆盖类定义中的默认setattr:

class Test:
    def __init__(self):
        self.a=5
    def __setattr__(self,name,value):
        print "Possibility disabled for the sake of this test"

test=Test() #prints the message from the custom method called inside __init__

但是,似乎无法在运行时覆盖setattr:

class Test:
    def __init__(self):
        self.a=5

test=Test()

import types
def __setattr__(self,name,value):
    print "Possibility disabled for the sake of this test"
test.__setattr__ = types.MethodType(__setattr__, test)
test.a=10 #does the assignment …