On Tue, Jan 31, 2012 at 5:53 PM, Chris Angelico <ros...@gmail.com> wrote: > On Wed, Feb 1, 2012 at 9:03 AM, Duncan Booth > <duncan.booth@invalid.invalid> wrote: >> Abitrarily nested tuples of exceptions cannot contain loops so the code >> simply needs to walk through the tuples until it finds a match. > > Is this absolutely guaranteed? The C API for CPython provides: > (Py2) http://docs.python.org/c-api/tuple.html#PyTuple_SetItem > (Py3) http://docs.python.org/dev/c-api/tuple.html#PyTuple_SetItem > > which doesn't have massive warnings on it saying "USE THIS ONLY TO > INITIALIZE A TUPLE" (compare, for instance, _PyTuple_Resize which does > carry a similar warning). Is the assumption then that we're all > adults, and that mutating a tuple is like passing a null pointer to an > API function (aka "loaded gun in proximity to foot")?
I don't know why the docs are written the way that they are, but if you check the code, you can see that PyTuple_SetItem will raise a SystemError if the reference count is anything other than 1. So I think that it is only meant to be used with similar caution and restraint. Cheers, Ian -- http://mail.python.org/mailman/listinfo/python-list
