"Jeff Shannon" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > [My newsreader crapped out on sending this; apologies if it appears > twice.] > > George Sakkis wrote: > > > "Terry Reedy" <[EMAIL PROTECTED]> wrote in message > > news:[EMAIL PROTECTED] > > > >>Aside from the problem of not being able to delete the underlying object, > >>the view object for a tuple would have to be a new type of object with a > >>new set of methods. > > > > It *could*, but it doesn't have to. One can represent a view as essentially > > an object with a pointer > > to a memory buffer and a (start,stop,step) triple. Then a "real tuple" is > > just a "view" with the > > triple being (0, len(sequence), 1). > > Except that that's not how Python tuples *are* constructed, and it'd > be a pretty big deal to redo the architecture of all tuples to support > this relatively special case. > > Even if this re-architecting were done, you're still constructing a > new object -- the difference is that you're creating this > (start,stop,step) triple instead of duplicating a set of PyObject* > pointers, and then doing math based on those values instead of > straightforward pointer access. I'm not at all convinced that this > really saves you a significant amount for tuple slices (really, you're > still constructing a new tuple anyhow, aren't you?), and it's going to > cost a bit in both execution time and complexity in the common case > (accessing tuples without slicing). If there's a big cost in object > construction, it's probably going to be the memory allocation, and for > a reasonable tuple the size of the memory required is not going to > significantly affect the allocation time. > > Jeff Shannon > Technician/Programmer > Credit International >
You're probably right about the allocation time, but my main concern is the memory required for each slice, which can be O(n) wrt the length of the whole tuple. I would like this to be constant (at least if there was a way around to the problem of deleting the underlying sequence). George -- http://mail.python.org/mailman/listinfo/python-list
