[Tutor] Distinction between tuples and lists

[Alan Gauld]

"Kent Johnson" <kent37 at tds.net> wrote
>
> For what it's worth, Guido has explicitly said,
> "Tuples are for heterogeneous data, list are for homogeneous data.
> Tuples are *not* read-only lists."

That surprises me, he has always seemed more pragmatist than purist.
However even Guido saying it doesn't alter the fact that in practice 
it
is not a part of the language, merely a usage pattern. (Of course that
could change in future versions like Python3000 but in the current
incarnation, we have what we have)

> Personally, I take this with a grain of salt. I do tend to use 
> tuples
> for things that are like records or structs, or often just for pairs
> of data (e.g. the elements of dict.items()), and lists for 
> homogeneous
> collections, but that is more a matter of fitness for the purpose 
> than
> dogma.

Precisely. That was the point I tried to make earlier that in most
usage scenarios lists tend to be used homogenously and tuples
heterogenenously. But there is absolutely nothing in Python that
mandates it. A good example of a homogenous tuple is a pair of
values such as a point's x,y coordinates. And heterogenuous lists
are also very useful at times, particularly when the only alternative
would be to define a singleton class...

Alan G.