[Python-Dev] very slow compare of recursive objects

[Tim Peters]

[Jeff Epler]
> Is this an example of the elusive "recursive tuple"?

It's an example of a tuple subclass; we already have examples of recursive
tuples (without subclassing).

> class X(tuple):
>     def __getitem__(self, idx):
>         if idx == 0: return self
>         return tuple.__getitem__(self, idx)
>
>     def __len__(self):
>         return min(1, tuple.__len__(self))
>
> >>> x = X([None])
> >>> print len(x), x[0] is x, x==x
> 1 True True
> >>> print x
> (None,)
>
> I'm also a bit confused by the last line.  I guess the builtin
> tuple.__repr__ uses the C-level API to access tuple items, not the real
> __getitem__ slot?  pprint shows the same thing, though.

It's off-topic for me.  You have the source code <wink>.  The key to both is
likely what happens when doing

for y in x:
    print y