How about "pure virtual methods"?

[Doug Holton]

> Noam Raphael wrote:
> even in the best solution that I know of, 
>> there's now way to check if a subclass has implemented all the 
>> required methods without running it and testing if it works. 

I think there are some solutions like PyProtocols, see section 2.2 on 
this page: http://www.python.org/cgi-bin/moinmoin/MetaClasses

But what you are wanting is used more in statically typed languages. 
If you want interfaces, abstract classes and virtual methods in a 
python-like language see boo: http://boo.codehaus.org/
It will catch errors like this at compile-time.