[Python-Dev] object capability; func_closure; __subclasses__
Phillip J. Eby
pje at telecommunity.com
Thu Jun 28 19:26:28 CEST 2007
At 05:23 PM 6/28/2007 +0100, tav wrote:
>Any pointers on removing members via ctypes front?
>
>Whilst I can understand even the most obscure aspects of your python
>code fine, I'm not familiar with C/ctypes...
What you want is to get access to the type's real dictionary, not the
proxy. Then you can just delete '__subclasses__' from the dictionary
using Python code. Here's some code that does the trick:
from ctypes import pythonapi, POINTER, py_object
getdict = pythonapi._PyObject_GetDictPtr
getdict.restype = POINTER(py_object)
getdict.argtypes = [py_object]
def dictionary_of(ob):
dptr = getdict(ob)
if dptr and dptr.contents:
return dptr.contents.value
'dictionary_of' returns either a dictionary object, or None if the
object has no dictionary. You can then simply delete any unwanted
contents. However, you should *never use this* to assign __special__
methods, as Python will not change the type slots correctly. Heck,
you should probably never use this, period. :) Usage example:
print "before", type.__subclasses__
del dictionary_of(type)['__subclasses__']
print "after", type.__subclasses__
This will print something like:
before <method '__subclasses__' of 'type' objects>
after
Traceback (most recent call last):
File "ctypes_dicto.py", line 14, in <module>
print "after", type.__subclasses__
AttributeError: type object 'type' has no attribute '__subclasses__'
et voila.
You should also be able to delete unwanted function type attributes like this::
from types import FunctionType
del dictionary_of(FunctionType)['func_closure']
del dictionary_of(FunctionType)['func_code']
Of course, don't blame me if any of this code fries your computer and
gives you a disease, doesn't work with new versions of Python, etc.
etc. It works for me on Windows and Linux with Python 2.3, 2.4 and
2.5. It may also work with 3.0, but remember that func_* attributes
have different names there.
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