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[Python-ideas] Support other dict types for type.__dict__

Eric Snow ericsnowcurrently at gmail.com
Mon Feb 27 20:18:05 CET 2012 
On Mon, Feb 27, 2012 at 11:45 AM, Mark Janssen
<dreamingforward at gmail.com> wrote:
> On Mon, Feb 27, 2012 at 11:35 AM, Rob Cliffe <rob.cliffe at btinternet.com> wrote:
>> I suggested a "mutable" attribute some time ago.
>> This could lead to finally doing away with one of Python's FAQs: Why does
>> python have lists AND tuples?  They could be unified into a single type.
>> Rob Cliffe.
>
> Yeah, that would be cool.  It would force (ok, *allow*) the
> documenting of any non-mutable attributes (i.e. when they're mutable,
> and why they're being set immutable, etc.).
>
> There an interesting question, then, should the mutable bit be on the
> Object itself (the whole type) or in each instance....?  There's
> probably no "provable" or abstract answer to this, but rather just an
> organization principle to the language....

In contrast to a flag on objects, one alternative is to have a
__mutable__() method for immutable types and __immutable__() for
mutable types.  I'd be nervous about being able to make an immutable
object mutable at an arbitrary moment with the associated effect on
the hash of the object.

-eric
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