New statement proposal for Python

[Nick Perkins]

"Alex Martelli" <aleaxit at yahoo.com> wrote in message >

<snip excellent comments re: 'constants'>

> ...
> One (IMHO) Python enhancement would be to give dictionaries
> some finer-grained control on their degree of mutability.
> The ability to selectively make SOME existing keys non
> rebindable and/or non removable _would_ come in handy in
> quite a few places ('constants' included), as would the
> related ones of locking a dictionary against addition of
> new keys.  Since ALMOST all Python namespaces are in fact
> dictionaries (local-variables of functions being the
> signal exception), such locking would give the basic
> semantics for several desirable tricks.
> ...

now, that's an interesting idea.
how would that look, syntactically?

dict['A']=1
dict.lock('A')

..making the value unchangeable?

..and would attempts to set the value raise an exception?