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

[Moshe Zadka]

On Wed, 29 Mar 2000, Peter Funk wrote:

> > 1. I tshouldn't share implementation with UserString, otherwise your
> > algorithm are not behaving with correct big-O properties. It should
> > probably use a char-array (from the array module) as the internal
> > representation.
> 
> Hmm.... I don't understand what you mean with 'big-O properties'.  
> The internal representation of any object should be considered ...
> umm ... internal.

Yes, but
s[0] = 'a'

Should take O(1) time, not O(len(s))

> > 2. It shouldn't share interface iwth UserString, since it doesn't have a
> > proper implementation with __hash__.
> 
> What's wrong with my implementation of __hash__ raising a TypeError with
> the attribution 'unhashable object'. 

A subtype shouldn't change contracts of its supertypes. hash() was
implicitly contracted as "raising no exceptions".


--
Moshe Zadka <mzadka@geocities.com>. 
http://www.oreilly.com/news/prescod_0300.html
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