[Python-Dev] Making mutable objects readonly

Guido van Rossum guido@digicool.com
Mon, 29 Jan 2001 21:17:27 -0500

> For different reasons, I'd like to be able to set a constant flag on a
> object instance.  Simple semantics: if you try to assign to a
> member or method, it throws an exception.
> Application?  I have a large Python program that goes to a lot of effort
> to build elaborate context structures in core.  It would be nice to know
> they can't be even inadvertently trashed without throwing an exception I 
> can watch for.

Yes, this is a good thing.  Easy to do on lists and dicts.  Questions:

- How to spell it?  x.freeze()?  x.readonly()?

- Should this reversible?  I.e. should there be an x.unfreeze()?

- Should we support something like this for instances too?  Sometimes
  it might be cool to be able to freeze changing attribute values...

--Guido van Rossum (home page: http://www.python.org/~guido/)