Result of ``a is b''

[Ronald Oussoren]

On 18-mrt-04, at 14:14, Axel Boldt wrote:

> afriere at yahoo.co.uk (Asun Friere) wrote
>> axelboldt at yahoo.com (Axel Boldt) wrote
>
>>>                                      Why would anybody ever want to
>>> know whether two strings or tupels are internally stored at the same
>>> location, other than to deduce details of the Python implementation?
>>
>> Most obviously to tell whether they are the same object or not.
>> While this is not an issue with simple strings, have you considered
>> what effect your suggestions would have on classes inheriting from
>> str?
>
> Indeed I have not. Probably because basic built-in strings form a type
> that's not a class and you can't inherit from it.

Yes you can:

Python 2.3 (#1, Sep 13 2003, 00:49:11)
[GCC 3.3 20030304 (Apple Computer, Inc. build 1495)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
 >>> class MyStr(str): pass
...
 >>> x = MyStr("hello")
 >>> type(x)
<class '__main__.MyStr'>
 >>>