> I like the definition of __sizeof__ that was discussed some time ago:
> http://bugs.python.org/issue14520#msg157798

The problem is that that definition isn't helpful.
If we ever change itertools.tee to use non-PyObjects internally, suddenly
its sys.getsizeof() would have to return much larger numbers despite
visible behaviour not having changed at all (and despite the memory
overhead being actually lower).

And gc.get_referents() is really a low-level debugging tool, certainly
not a "reflection API" (inspect would serve that role).