Duncan Booth wrote:
Is there any reason why tuples need to throw an exception on assigning to the element if the old value and new value are the same object?
It would make introspection misleading, because tuples would have a __setitem__ method event though they don't actually support item assignment. Also, it would solve the problem for tuples in particular, but not for any other immutable type -- they would all have to implement the same behaviour independently to enjoy the benefit. Here's another idea: If the __iadd__ method returns the same object, *and* the LHS doesn't have a __setitem__ method, then do nothing instead of raising an exception. Peter Otten wrote: > Traceback (most recent call last): > File "<stdin>", line 2, in <module> > File "<stdin>", line 4, in __setitem__ > TypeError: 257 is not 257 > > I'm not sure "help" is the right word here ;) I don't think that's a problem, because the use case being addressed is where the object performs in-place modification and always returns itself. Any object that doesn't return itself is not modifying in-place, even if the returned object happens to be equal to the original one. -- Greg -- https://mail.python.org/mailman/listinfo/python-list
