Marc 'BlackJack' Rintsch <bj_...@gmx.net> writes: > On Fri, 12 Dec 2008 07:56:58 -0800, sturlamolden wrote: > >> On Dec 12, 4:55 pm, sturlamolden <sturlamol...@yahoo.no> wrote: >> >>> def __setitem__(self, index, value): >>> if _buf[index] is not value: # given that _buf is the tuple's >>> internal buffer >>> raise TypeError, 'tuple' object does not support item >>> assignment >> >> blæh, that should be self._buf[index] > > But then the error message is not true anymore because tuples *would* > support item assignment when the old and new value are the same. Which > leads to strange things like code that may or may not raise that > exception, depending on implementation details: > > t = (1, 2) > t[0] = 1 # Maybe okay -- maybe not. > t[1] += 0 # Same here. > > I'd find that quite odd. > > Ciao, > Marc 'BlackJack' Rintsch
What I find a bit annoying is when you get both * an exception * a mutation E.g. >>> t[1] *= 2 Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'tuple' object does not support item assignment Now is t the same as before? Sometimes it is: >>> t (1, 2) >>> t[1] *= 2 Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'tuple' object does not support item assignment >>> t (1, 2) Sometimes not: >>> t (1, [2]) >>> t[1] *= 2 Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'tuple' object does not support item assignment >>> t (1, [2, 2]) I agree it's not a bug, but I never feel comfortable with it. -- Arnaud -- http://mail.python.org/mailman/listinfo/python-list
