On 2007-08-11, Alex Martelli <[EMAIL PROTECTED]> wrote: > Neil Cerutti <[EMAIL PROTECTED]> wrote: > ... >> The Python Language Reference seems a little confused about the >> terminology. >> >> 3.4.7 Emulating numeric types >> 6.3.1 Augmented assignment statements >> >> The former refers to "augmented arithmetic operations", which I >> think is a nice terminology, since assignment is not necessarily >> taking place. Then the latter muddies the waters. > > Assignment *IS* "necessarily taking place"; if you try the augmented > assignment on something that DOESN'T support assignment, you'll get an > exception. Consider: > >>>> tup=([],) >>>> tup[0] += ['zap'] > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > TypeError: 'tuple' object does not support item assignment > > Tuples don't support item ASSIGNMENT, and += is an ASSIGNMENT, > so tuples don't allow a += on any of their items. > > If you thought that += wasn't an assignment, this behavior and > error message would be very problematic; since the language > reference ISN'T confused and has things quite right, this > behavior and error message are perfectly consistent and clear.
Thanks for the correction. I was under the illusion that sometimes augmented assignment would instead mutate the object. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
