Inheriting the str type

[Andrew Bennetts]

On Tue, Feb 04, 2003 at 04:23:24PM +1300, Mike McGavin wrote:
> 
> Following up on my query 24 hours ago about CGI and database-friendly 
> string manipulation modules, I've been experimenting with writing my 
> own. So far I've made a class which acts in a similar way to python's 
> str type with a few extras.  I'd like to inherit the python 'str' type 
> as a base class, but I've been unsuccessful because of a problem that 
> I've encountered.

The str type is immutable, so to subclass it you probably need to use
__new__.

[..snip..]
> 
> Without inheriting I can still make my class act almost the same as 
> python's 'str' type, but I'd like to inherit it if possible. Otherwise 
> any code that checks that a parameter is a 'str' type breaks, unless 
> there's an explicit conversion made back to a python string.

In theory, Pythonic code won't care if something is a string, but simply if
it behaves more-or-less like a string.  Inheritance isn't necessarily the
right way for a class to say "I implement this behaviour".

-Andrew.