I missed that you would use it with the idiom: dct[x.frozen()]
The list itself isn't hashable with this approach, so you don't have much choice. I wasn't particularly clear about that point, though.
I have two problems with this approach.
1) It doesn't work when you get your keys via the keys/items methods.
True - the frozen object has no link back to the original object. That could be added though (by returning a tuple subtype with the extra attribute)
2) This is rather minor, but a user could still unfreeze
untimely
True - doing that is less likely than mutating a hashable list though :)
I'm just noting this as a way to avoid copying data more than once when storing immutable copies of mutable data in a dictionary. You're quite right that there isn't a really clean idiom for doing that in Python (aside from moving to a different data structure that works natively as a dict key, naturally).
Cheers, Nick.
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Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia
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http://boredomandlaziness.skystorm.net
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