Library Reference 2.1 under property():

class C(object):
   def __init__(self): self.__x = None

__x should be _x

Thanks for the report!

It looks like this was previously reported in issue #1575746, and has 
been fixed in the 2.5 maintenance branch and the trunk.  Python 2.5.2 
should be out any day now; the fix should then hit docs.python.org.

I tried to search for a prior report with no success. How should I have 
done tha

I'm guessing that you used the 'search in open issues' box at the top 
right.  Of course, the problem is that this issue was already closed.

Instead, go to 'Search' on the left-hand side under 'Issues', enter 
'property' and '__x' into the 'All text' box, select 'don't care' as the 
status, and try the search again...

...and you'll see that you're not the only person to have rereported this!

In any case, better to have multiple reports that none at all.

I should have added:

You can also check the in-development version of the documentation at

docs.python.org/dev

to see if it's already been fixed.