Sorry for not responding for so long, I didn't work on Python through the summer because of some other matters.

Re-execution of the module is not possible, because there is a check on the C level, If you call exec_in_module() on an already initialized module, it'll raise ImportError.

Also, because of this check, there is the restriction for py_mod_create. "Modules" defining this slot might not be module objects at all, so they might not have the module state pointer (which is used to flag if the module was initialized).