[PyQt] [SIP] How to reasonably implement writable global variables?

[Phil Thompson]

On Wed, 3 Jul 2013 00:28:59 +0800, "Casper Ti. Vector"
<caspervector at gmail.com> wrote:
> Hello list, I am a newcomer to SIP (only one day experience), and please
> tell me if I make a mistake.  Thanks :)
> 
> I found it quite hard to make read-write interface for (module-wide)
> global variables (other than explicitly writing C/C++ functions to get
and
> set them).  For example:
> 
> test.sip:
>> %Module test
>> %ModuleHeaderCode
>> #include "test.h"
>> %End
>> 
>> int test;
>> int get_test(void);
>> void set_test(int x);
> 
> test.h:
>> extern int test;
>> int get_test(void);
>> void set_test(int x);
> 
> test.cpp:
>> int test = 0;
>> int get_test(void) {
>>   return test;
>> }
>> void get_test(int x) {
>>   test = x;
>> }
> 
> test.py:
>> import test
>> print(test.test) # 0
>> print(test.get_test()) # 0
>> test.set_test(1)
>> print(test.test) # 0
>> print(test.get_test()) # 1
>> test.test = 2
>> print(test.test) # 2
>> print(test.get_test()) # 1
> 
> Thus `test' in python seems to be totally independently from its C++
> counterpart once it is formed.  However, if wrapped in a class, they
> would be bound together, and changes in one will affect the other.
> 
> So is there any elegant way to make global variables writable using
> the `var = val' syntax?  Any suggestions are welcome :)
> 
> P.S. I know python is object-oriented, but I think this particular
>      approach is still pratically useful in some situations (and OOP
>      itself is not a "silver bullet"), so it might not be meaningless to
>      implement this.

You can't do it. Python needs to support module level descriptors for it
to be implemented.

Phil