Question

I have a structure as below

class DEVINFO(Structure):
       _fields_ = [("szDeviceName", c_char*MAX_PATH),                                           
                   ("pDevExtension", POINTER(DEVEXTENSION))]

In the above, DEVEXTENSION structure is as follows

class DEVEXTENSION(Structure):
            _fields_ = [("szProductName",c_char*MAX_PATH),
                        ("szManfName",c_char*MAX_PATH),
                        ("szSerialNumber",c_char*32)]

My question is how would i access the members of “DEVEXTENSION” structure.

devInfo = DEVINFO()
devInfo.szDeviceName = "USB Flash 302"
print(devInfo.szDeviceName)

Answer 1

From the ctypes tutorial:

Pointer instances have a contents attribute which returns the object
to which the pointer points

So, devInfo.pDevExtensions.contents.szProductName for example, presuming that DEVINFO will produce an instance of DEVEXTENSION – to me, it isn’t obvious it does here (but I’m not familiar with ctypes).

Also note that PEP-8 recommends CapWords for class names, and CAPS to be reserved for constants.