> Charles gave this example of code that would fall over:
>
> size = 0
> for name, st in scandir(path):
>     if stat.S_ISREG(st.st_mode):
>         size += st.st_size
>
> I don't see it, though. In this case you need both .st_mode and .st_size, so a caller would check that those are not None, like so:

Well, that's precisely the point.
A normal "caller" would never expect a stat object to be partially
populated: if a function has a prototype returning a stat object, then
I definitely expect it to be a regular stat object, with all the
fields guaranteed by POSIX set (st_size, st_ino, st_dev...). By
returning a dummy stat object, you break the stat interface, and I'm
positive this *will* puzzle users and introduce errors.

Now, if I'm the only one who finds this trick dangerous and ugly, you
can go ahead, but I stand by my claim that it's definitely a bad idea
(between this and the explicit Enum value assignent, I feel somewhat
lost lately :-)