On Fri, Nov 21, 2014 at 10:39 AM, <random...@fastmail.us> wrote: > On Fri, Nov 21, 2014, at 02:00, Marko Rauhamaa wrote: >> Gill Shen <gillar...@gmail.com>: >> >> > How is this [nesting] behavior implemented under the hood? >> >> Pointers. >> >> > And why is this allowed at all? >> >> There's no reason not to. > > There's no reason not to allow it with tuples, but you can't do it. > Mainly because doing it in a single literal would require special > syntax, whereas you can simply append to a list a reference to itself. > > I think I tried on at least one python version and printing the tuple > crashed with a recursion depth error, since it had no special protection > for this case the way list printing does.
Here's a nice crash. I thought this might similarly produce a recursion depth error, but no, it's a seg fault! $ cat test.py import itertools l = [] it = itertools.chain.from_iterable(l) l.append(it) next(it) $ python3 test.py Segmentation fault (core dumped) -- https://mail.python.org/mailman/listinfo/python-list
