How can I make an existing object read-only?

[Duncan Booth]

Alex Martelli wrote:

> Irmen de Jong <irmen at -nospam-remove-this-xs4all.nl> wrote:
> 
>> Maybe I'm way off track here, but I want to do something like this:
>> 
>> Say I have an object that's initialized with a bunch of attributes.
>> I want to pass the object to a piece of code that is not allowed
>> to add/delete/set attributes on this object.
>> When control returns, the code is again allowed to make changes
>> to the object.
> 
> Instead of passing the bare object, pass it wrapped into something like:
> 
<snip>

An alternative is just to pass a copy of the object. That way the recipient 
can do what they like with it, but the calling code won't see any changes.