[Python-Dev] [1.6]: UserList, Dict: Do we need a UserString class?

[Moshe Zadka]

On Wed, 29 Mar 2000, Guido van Rossum wrote:

> Let's not confuse subtypes and subclasses.  One of the things implicit
> in the discussion on types-sig is that not every subclass is a
> subtype!  Yes, this violates something we all learned from C++ -- but
> it's a great insight.  No time to explain it more, but for me, Peter's
> subclassing UserString for MutableString to borrow implementation is
> fine.

Oh, I agree with this. An earlier argument which got snipped in the
discussion is why it's a bad idea to borrow implementation (a totally
different argument)

--
Moshe Zadka <mzadka@geocities.com>. 
http://www.oreilly.com/news/prescod_0300.html
http://www.linux.org.il -- we put the penguin in .com