python assemble methods at runtime?

在以前曾经讨论过一个例子：python unzip，当时在外部定义了一个函数，然后直接利用 setattr 将其加入到 ZipFile 类对象中，如下：

>>> class test:
...     pass
...
>>> def func(self):
...     print self.__dict__
...
>>> test.func = func
>>> t = test()
>>> t.func()
{}
>>>

但是，如果在类定义中直接使用，则不行：

>>> def func(self):
...     print self.__dict__
...
>>> class test:
...     def __init__(self):
...             self.func = func
...
>>> t = test()
>>> t.func()
Traceback (most recent call last):
  File "", line 1, in 
TypeError: func() takes exactly 1 argument (0 given)

使用 setattr 也不行：

>>> def func(self):
...     print self.__dict__
...
>>> class test:
...     def __init__(self):
...             setattr(self, 'func', func)
...
>>> t = test()
>>> t.func()
Traceback (most recent call last):
  File "", line 1, in 
TypeError: func() takes exactly 1 argument (0 given)

但是，是不是我放在外面定义就没有一点问题了呢？在 mirrord.py 中，我就希望在运行时再装配，因为直接在 __init__ 中定义不行，所以我这样做：

def _schedule_thread(self, Server, address):
    that = threading.Thread(
        target=self.__run_schedule, name='schedule', args=(Server, address))
    that.setDaemon(1)
    that.start()
    that.join() 

def _schedule_process(self, Server, address):
    """
    There is a sharing problem has not been solved:
    manager(WatchManager) should be shared among processes
    """
    pid = os.fork()
    if pid == 0: self.__run_schedule(Server, address)

class Mirrord:
    ...
    def __run_schedule(self, Server, address):
    ...
Mirrord._schedule = _schedule_thread

结果在测试的时候报错：

Exception in thread mirrord:
Traceback (most recent call last):
  File "/usr/lib/python2.5/threading.py", line 460, in __bootstrap
    self.run()
  File "/usr/lib/python2.5/threading.py", line 440, in run
    self.__target(*self.__args, **self.__kwargs)
  File "mirrord_ut.py", line 56, in __run_thread
    self.mrd.run(('localhost', 2123))
  File "/root/ulfs/cutils/trunk/lib/mirrord.py", line 497, in run
    self._schedule(Server, address)
  File "/root/ulfs/cutils/trunk/lib/mirrord.py", line 380, in _schedule_thread
    target=self.__run_schedule, name='schedule', args=(Server, address))
AttributeError: Mirrord instance has no attribute '__run_schedule'

，而如果将那两个函数改为：

def _schedule_thread(self, Server, address):
    that = threading.Thread(
        target=self._Mirrord__run_schedule, name='schedule', args=(Server, address))
    that.setDaemon(1)
    that.start()
    that.join() 

def _schedule_process(self, Server, address):
    """
    There is a sharing problem has not been solved:
     manager(WatchManager) should be shared among processes
    """
    pid = os.fork()
    if pid == 0: self._Mirrord__run_schedule(Server, address)

则可以通过。但显然使用 _Mirrord__run_schedule 这种方式看上去不是太好！