tuple versus list

[Bryan]

>>
>>i always use the structure analogy.  if you view (width, height) as a 
>>structure, 
>>use a tuple.  if you view it a sequence, use a list.  in this example, i view 
>>it 
>>as a stucture, so i would use (width, height) as a tuple.
> 
> 
> Right, but there's an unfortunate ambiguity in the term "sequence",
> since in Python it is defined to include tuple.  I gather you meant
> more in the abstract sense of a data collection whose interesting
> properties are of a sequential nature, as opposed to the way we are
> typically more interested in positional access to a tuple.  Maybe
> a more computer literate reader will have a better word for this,
> that doesn't collide with Python terminology.  My semi-formal
> operational definition is "a is similar to a[x:y], where
> x is not 0 or y is not -1, and `similar' means `could be a legal
> value in the same context.'"
> 
>    Donn Cave, donn at u.washington.edu


yes, you are correct.  i shouldn't have used the word "sequence" which is a 
python term.   maybe structure vs. array.  in any case, i think the *wrong* 
answer that is often given to this question is along the lines of if it's read 
only, make it a tuple. if it's read write, make it a list. a great trivial 
example is a point.  a point is a structure (x, y).  if you have many points 
then you have a list of structures: [(x, y), (x1, y1), (x2, y2), ...].  to me, 
it doesn't matter if you want to modify a point.  if you do then create a new 
one, but don't make it a list just to make it modifiable.

bryan