Win32 dll / ctypes question

[Thomas Heller]

Even more interesting is to follow the 'ob_type' member
field of Python objects, which is possible with this code:

--------
from ctypes import windll, Structure, POINTER, SetPointerType

PTYPE = POINTER("PythonType")

class PythonObject(Structure):
    _fields_ = [
        ("ob_refcnt", "i"),
        ("ob_type", PTYPE)]

class PythonType(Structure):
    _fields_ = [
        ("ob_refcnt", "i"),
        ("ob_type", PTYPE),
        ("ob_size", "i"),
        ("tp_name", "z"),
        ("tp_basicsize", "i"),
        ("tp_itemsize", "i"),
        ("tp_dealloc", "i"),
        ("tp_print", "i"),
        ("tp_getattr", "i"),
        ("tp_setattr", "i"),
        ("tp_compare", "i"),
        # and so on...
        ]

SetPointerType(PTYPE, PythonType)

for obj in (42, 1.2, (), [], {}, int, PythonType):
    p = PythonObject.from_address(id(obj))
    t = p.ob_type.contents
    print repr(obj), t.tp_basicsize, t.tp_itemsize, t.tp_name
--------

The output of the script is:

42 12 0 int
1.2 16 0 float
() 12 4 tuple
[] 16 0 list
{} 124 0 dict
<type 'int'> 436 20 type
<class '__main__.PythonType'> 436 20 _ctypes.StructType

Thomas