[Python-Dev] Add a frozendict builtin type (original) (raw)

Mark Shannon mark at hotpy.org
Tue Feb 28 13:07:32 CET 2012

Antoine Pitrou wrote:

On Tue, 28 Feb 2012 12:45:54 +0100 Victor Stinner <victor.stinner at haypocalc.com> wrote:

I think you need to elaborate on your use cases further, ... A frozendict can be used as a member of a set or as a key in a dictionary.

For example, frozendict is indirectly needed when you want to use an object as a key of a dict, whereas one attribute of this object is a dict. It isn't. You just have to define hash correctly. frozendict helps also in threading and multiprocessing. How so?

Inter process/task communication requires copying. Inter/intra thread communication uses reference semantics. To ensure these are the same, the objects used in communication must be immutable.

Cheers, Mark.

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