@Swapnil: the rules you quote are correct for the C extension, but do not apply when using ctypes, because ctypes is doing the required initializations automatically.

However, if Amaury is correct, ctypes performs the initializations in a way that break the threading.local functionality. 

I think the best way to address this bug would therefore be to add a warning to the ctypes documentation that C created threads will not support threading.local().