Programmiererforum

Nur so geradlinig, scheint in Python nicht zu funktionieren. < /p>
import ctypes

class cA(ctypes.Structure):
_fields_ = [("a", ctypes.c_ubyte)]

def __init__(self):
super().__init__()
self.c = 3

z = cA.from_buffer_copy(b'0')
print (z)
print (z.c)
print (dir(z))
< /code>
Traceback (most recent call last):
File "polymorph.py", line 12, in
print (z.c)
AttributeError: 'cA' object has no attribute 'c'
< /code>
So ctypes.Structure factory classmethod from_buffer_copy() doesn't seem to use the default constuctor __init__ .
Is this correct and intended by cytpes.Strucutre?
Ok even if not trying to workaround this, by overwriting the class method from_buffer_copy raises another issue.
Like adding to class cA:
@classmethod
def from_buffer_copy(cls,buffer, offset=0):
#obj = super().from_buffer_copy(b'2',offset)
obj = cls.from_buffer_copy(b'2',offset)
obj.__init__()
return obj
< /code>
Traceback (most recent call last):
File "polymorph.py", line 17, in
z = cA.from_buffer_copy(b'0')
File "polymorph.py", line 13, in from_buffer_copy
obj = cls.from_buffer_copy(b'2',offset)
File "polymorph.py", line 13, in from_buffer_copy
obj = cls.from_buffer_copy(b'2',offset)
File "polymorph.py", line 13, in from_buffer_copy
obj = cls.from_buffer_copy(b'2',offset)
[Previous line repeated 996 more times]
RecursionError: maximum recursion depth exceeded
< /code>
This creates a RecursionError, because same class method is called again and again, but Structure.from_buffer_copy can't be called either, because it lacks the fields.
Using super() above doesn't helps either. It raises an Attribute Error:
Traceback (most recent call last):
File "polymorph.py", line 17, in
z = cA.from_buffer_copy(b'0')
File "polymorph.py", line 12, in from_buffer_copy
obj = super().from_buffer_copy(b'2',offset)
AttributeError: 'super' object has no attribute 'from_buffer_copy'
< /code>
This seems to be similar to Using super with a class method
Looks like a special python 3 thing either.
So cytypes.Structure seems to be a real special kind of class.
As doing the same with regular python class is no issue.
Like:
import ctypes

class A:
def __init__(self):
self.a = "Tex"

@classmethod
def factory(cls):
return cls()

class B(A):
def __init__(self):
super().__init__()
self.b = "bTex"

z = B.factory()
print (z)
print (z.b)
print (dir(z))

< /code>
So ... Is there a way to mix ctypes.Structure with regular python class fields or better just don't do it and better embed ctypes.Structure inside other regular classes for this just to work around this?