[Python-Dev] Add a frozendict builtin type

[Mark Shannon]

Victor Stinner wrote:
>>>  * frozendict values must be immutable, as dict keys
>> Why?  That may be useful, but an immutable dict whose values
>> might mutate is also useful; by forcing that choice, it starts
>> to feel too specialized for a builtin.
> 
> Hum, I realized that calling hash(my_frozendict) on a frozendict
> instance is enough to check if a frozendict only contains immutable
> objects. And it is also possible to check manually that values are
> immutable *before* creating the frozendict.
> 
> I also prefer to not check for immutability because it does simplify
> the code :-)
> 
> $ diffstat frozendict-3.patch
>  Include/dictobject.h   |    9 +
>  Lib/collections/abc.py |    1
>  Lib/test/test_dict.py  |   59 +++++++++++
>  Objects/dictobject.c   |  256 ++++++++++++++++++++++++++++++++++++++++++-------
>  Objects/object.c       |    3
>  Python/bltinmodule.c   |    1
>  6 files changed, 295 insertions(+), 34 deletions(-)
> 
> The patch is quite small to add a new builtin type. That's because
> most of the code is shared with the builtin dict type. (But the patch
> doesn't include the documentation, it didn't write it yet.)
> 

Could you create an issue for this on the tracker, maybe write a PEP.
I don't think sending patches to this mailing list is the way to do this.

Would you mind taking a look at how your code interacts with PEP 412.

Cheers,
Mark.