On Nov 11, 2006, at 10:52 AM, Carl Karsten wrote:
> not to mention I still don't
> understand the difference between [1,2,3] and (1,2,3) even though
> I understand
> how to use them.
On the practical side, one is mutable and the other is fixed. If you
have a set of things that you need to add to, remove from, or
otherwise manipulate, use a list. Otherwise, use a tuple. Tuples have
much lower overhead.
The theoretical difference is more of a mathematical distinction
rather than a practical one. Remember, the BDFL is a mathematician.
He sees it as the difference between well-defined groupings and ad-
hoc collections of things. Consider a point in cartesian space: it is
defined by x-y-z coordinates. That would be best represented as a 3-
tuple. All such points have the same structure, and each position in
the tuple has a defined meaning. It makes no sense for such a tuple
to have an append() or remove() method, since by definition a point
in space is defined by those three numbers. And it makes no sense to
allow those values to change, because then it would no longer be the
same point.
However, a collection of things that is arbitrary is best
represented as a list. Let's take the people who will be at next
Tuesday's meeting. It is not defined in advance; people can show up
late or leave early, so it is expected that at any time, that group
will change. A list makes much more sense in this case.
Again, this is mostly theoretical; if you're not sure, use a list -
they are much more practical, and RAM and CPU cycles are cheap.
-- Ed Leafe
-- http://leafe.com
-- http://dabodev.com
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