[Python] Issue regarding overlap of memory allocation for separate dataclasses

I am experimenting with defining dataclasses for containing ctypes objects. I have defined three classes; two of which are used as attributes to the third:

@dataclasses.dataclass
class Point:
x = ctypes.c_int(0)
y = ctypes.c_int(0)

@dataclasses.dataclass
class Point2:
x = ctypes.c_int(0)
y = ctypes.c_int(0)

@dataclasses.dataclass
class TestObj:
point1 = Point()
point2 = Point()


The TestObj class is then passed to a C function inc:

#include <stdio.h>

void inc(int *x, int *y)
{
*x = *x + 1;
*y = *y + 1;
}


via a wrapper:

def inc(test: TestObj):
_inc = lib.inc

_inc.argtypes = [ctypes.POINTER(ctypes.c_int), ctypes.POINTER(ctypes.c_int)]
_inc.restype = None
_inc(test.point1.x,test.point1.y)


When investigating the result of the pass to inc I observe the snippet:

test = TestObj()
print(f"addressof test.point1.x = {ctypes.addressof(test.point1.x)}")
print(f"test.point1.x.value = {test.point1.x.value}")
print(f"addressof test.point1.y = {ctypes.addressof(test.point1.y)}")
print(f"test.point1.y.value = {test.point1.y.value}")
print(f"addressof test.point2.x = {ctypes.addressof(test.point2.x)}")
print(f"test.point2.x.value = {test.point2.x.value}")
print(f"addressof test.point2.y = {ctypes.addressof(test.point2.y)}")
print(f"test.point2.y.value = {test.point2.y.value}")
inc(test)
print("after pass to inc")
print(f"addressof test.point1.x = {ctypes.addressof(test.point1.x)}")
print(f"test.point1.x.value = {test.point1.x.value}")
print(f"addressof test.point1.y = {ctypes.addressof(test.point1.y)}")
print(f"test.point1.y.value = {test.point1.y.value}")
print(f"addressof test.point2.x = {ctypes.addressof(test.point2.x)}")
print(f"test.point2.x.value = {test.point2.x.value}")
print(f"addressof test.point2.y = {ctypes.addressof(test.point2.y)}")
print(f"test.point2.y.value = {test.point2.y.value}")


results in:

addressof test.point1.x = 124872721403536
test.point1.x.value = 0
addressof test.point1.y = 124872719995280
test.point1.y.value = 0
addressof test.point2.x = 124872721403536
test.point2.x.value = 0
addressof test.point2.y = 124872719995280
test.point2.y.value = 0
after pass to inc
addressof test.point1.x = 124872721403536
test.point1.x.value = 1
addressof test.point1.y = 124872719995280
test.point1.y.value = 1
addressof test.point2.x = 124872721403536
test.point2.x.value = 1
addressof test.point2.y = 124872719995280
test.point2.y.value = 1


the memory locations of the subsequent x and y attributes of each Point instance share the same memory location respectively and that the x and y attributes of each Point instance attributes of the TestObj instance are incremented, instead of just the point1 attributes.

If I redefine TestObj as:

@dataclasses.dataclass
class TestObj:
point1 = Point()
point2 = Point2()


and again pass it to the inc wrapper I observe the intended result of:

addressof test.point1.x = 133142487043728
test.point1.x.value = 0
addressof test.point1.y = 133142485635472
test.point1.y.value = 0
addressof test.point2.x = 133142485635728
test.point2.x.value = 0
addressof test.point2.y = 133142485635984
test.point2.y.value = 0
after pass to inc
addressof test.point1.x = 133142487043728
test.point1.x.value = 1
addressof test.point1.y = 133142485635472
test.point1.y.value = 1
addressof test.point2.x = 133142485635728
test.point2.x.value = 0
addressof test.point2.y = 133142485635984
test.point2.y.value = 0


While the x and y attributes of point1 and point2 share the same memory locations repspectively, now only the point1 x and y are incremented as intended.

I am puzzled as to how this is happening, given that in both scenarios the x and y attributes seemingly share the same memory location, but the change in name of the Point attribute provides the intended result. I appreciate any and all help in understanding what is happening.

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