On Thu, Oct 23, 2014 at 11:07 AM, Seymore4Head <Seymore4Head@hotmail.invalid> wrote: > BTW I forgot to add that example 2 and 3 don't seem to be too useful > in Python 3, but they are in Python 2. I don't understand how the > Python 3 is an improved version.
In Python 2, range returns a list containing all the requested elements. This is simple to work with but often not desirable, because it forces the entire sequence to be loaded into memory at once. Large ranges may cause excessive memory use and related slowdowns, while very large ranges may not even be usable. In Python 3, range returns a compact object that knows what elements it contains and can iterate over them (which is the most common use of ranges by far), but without needing to load them all into memory at once. While iterating, only the current element needs to exist in memory. You can still get the range as a list if you want it, by calling list(range(10)), but it doesn't force you to create a list, which makes it more versatile than the Python 2 construct. The more specialized data structure used in Python 3 also allows for certain optimizations, for example membership testing. In Python 2, if you do the test "97 in range(100)", it has to construct a 100-element list and then iterate over 97 of the elements before discovering that the list does in fact contain the number 97. The Python 3 range object knows what the bounds of the range are, so all it has to do is check that 0 <= 97 < 100 to know that the number 97 is included in the range. -- https://mail.python.org/mailman/listinfo/python-list
