ctypes:passing python class instances through c and back

[m2i3k]

Hi
I have C code with requires me to register a python callback. I am
able to get the callback working well using ctypes if I use global
functions without any context argument for the callback.

Now I want to register a python class member function for callback,
and give "self" as the context argument at the time of callback
registration. Then the c code can invoke the callback with self as the
context argument

class SomeClass(objec t):
def __init__(self):
self.msg = 'Hello'

def callbackMethod( context):
# self = somemagic(conte xt) <<<<<< how to convert this ptr
back to instance???
print self.msg

CALLBACK_FN_TYP E = WINFUNCTYPE(Non e,c_void_p)

s=SomeClass()
registerCallbac k(CALLBACK_FN_T YPE(s.callbackM ethod),py_objec t(self))

If I print context that comes in the callback, it is the address of
the instance 's'. Now how do I generate the class instance back from
the void* context that is passed into the callback?

[Gabriel Genellina]

En Thu, 26 Jul 2007 12:18:04 -0300, m2i3k <m2*******@gmai l.comescribió:

I have C code with requires me to register a python callback. I am
able to get the callback working well using ctypes if I use global
functions without any context argument for the callback.

Now I want to register a python class member function for callback,
and give "self" as the context argument at the time of callback
registration. Then the c code can invoke the callback with self as the
context argument

Use a bound method as the callback -that is, get the method from an
instance, not from the class-.
Pass it the same way as you would pass a global function; you get the
"self" argument for free :)

--
Gabriel Genellina