[Python-Dev] Making mutable objects readonly

[M.-A. Lemburg]

Mark Hammond wrote:
> 
> MAL writes:
> 
> > > - How to spell it?  x.freeze()?  x.readonly()?
> >
> > How about .lock() and .unlock() ?
> 
> I'm with Greg here - lock() and unlock() imply an operation similar to
> threading.Lock() - ie, exclusivity rather than immutability.
> 
> I don't have a strong opinion on the other names, but definately prefer any
> of the others over lock() for this operation.

Funny, I though that .lock() and .unlock() could be used to
implement exactly what threading.Lock() does...

Anyway, names really don't matter much, so how about: 

.mutable([flag]) -> integer

  If called without argument, returns 1/0 depending on whether
  the object is mutable or not. When called with a flag argument,
  sets the mutable state of the object to the value indicated
  by flag and returns the previous flag state.

The semantics of this interface would be in sync with many other
state APIs in Python and C (e.g. setlocale()).

The advantage of making this a method should be clear: it allows
writing polymorphic code.

-- 
Marc-Andre Lemburg
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