Python：从回调访问对象属性

Python: access to object attribute from callback

我正在尝试用回调函数设计类，该函数被传输到某个C库。需要在不更改回调参数的情况下授予对此类对象的访问权限。如何做到这一点？

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from ctypes import *
...
lib = CDLL('mylibname.so')
...
class A(object):
def __init__(self):
CALLBACK = CFUNCTYPE(c_uint32, c_void_p)
self.callback_func = CALLBACK(A.message_callback)
self.param = None
def message_callback(data):
... #here need access to self.param
return 0
def set_param(self, param):
self.param = param
...
a = A()
lib.lib_func(param1, param2, a.callback_func)

编辑：我已经用包装函数更改了类中的回调方法：

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from ctypes import *
...
lib = CDLL('mylibname.so')

class struct_t(Structure):
pass
struct_t._fields_ = [('next', POINTER(value_pair_t)),
('key', c_char_p),
('value', c_char_p)]
...
class A(object):
def __init__(self):
self.param = None

def wrapper(self):
CALLBACK = CFUNCTYPE(c_uint32, POINTER(struct_t))
def message_callback(data):
... # now I have access to self here
return 0
return CALLBACK(message_callback)

def set_param(self, param):
self.param = param
...
a = A()
lib.lib_func(param1, param2, a.wrapper())

它适用于python2，但我仍然对python3有问题：

回溯(最近一次呼叫的最后一次)："调用回调函数"中的文件"ctypes/callbacks.c"，第260行类型错误："lp结构"对象不可调用

以下是同一问题的链接：奇怪的bug？