Best way to enumerate classes in a module

[Terry Reedy]

Дамјан Георгиевски wrote:
> I need to programmaticaly enumerate all the classes in a given module. 
> Currently I'm using dir(module) but the Notice on the documentation page 
> [1]  says "dir() is supplied primarily as a convenience for use at an 
> interactive prompt" so that kind of scares me.

That notice primarily refers to the fact that the special names (of 
__xxx__ form) returned are implementation and version dependent, and may 
not be complete in the sense that dir(ob) may not return __xyz__ even 
though ob.__xyz__ exists and can be retrieved.

If you are only interested in regular-name attribute of ob, let your 
fear fly away.