Interning own classes like strings for speed and size?

[Christian Heimes]

Am 28.12.2010 21:16, schrieb Hrvoje Niksic:
> Christian Heimes <lists at cheimes.de> writes:
> 
>> Also this code is going to use much more memory than an ordinary tuple
>> since every instance of InternedTuple has a __dict__ attribute. This
>> code works but I had to move the cache outside the class because of
>> __slots__.
> 
> Wouldn't it work inside the class as well?  __slots__ applies to
> instances, not to classes themselves.  In Python 3.1:

You are right as long as you don't try to rebind the variable. I
recalled that class attributes of classes with __slots__ behave slightly
different than ordinary classes. For example you can't have a writeable
slot and class default values at the same time.

>>> class Example2(object):
...     __slots__ = ()
...     _cache = {}
...
>>> Example2()._cache
{}
>>> Example2()._cache = {}
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Example2' object attribute '_cache' is read-only

Christian