On Tue, 06 Nov 2007 11:25:29 +0000, Duncan Booth wrote:
> Steven D'Aprano <[EMAIL PROTECTED]> wrote:
>
>
>
>> Not quite, because that will also convert strings to tuples, which may
>> not be what you want for a general solution.
>
> I take it you didn't actually try the original code then.
No I didn't.
> Converting strings to tuples is not something it did.
Ah yes, you're right. The old "single characters are sequences too"
gotcha bites again.
>> That works for all data types I've tried, and it insures that the keys
>> it makes from different types are distinguishable:
>>
>> e.g.
>>
>> make_dict_key([(1, 2), (3, 4)]) != make_dict_key({1: 2, 3: 4})
>
> Really? It seems to me to be quite easy to get a clash:
>
>>>> make_dict_key([])
> (<type 'list'>,)
>>>> make_dict_key((list,))
> (<type 'list'>,)
I should have said "tries to insure". It isn't strictly possible to avoid
all clashes, even in principle. For any mutable object M, if make_dict_key
(M) returns a key K, then make_dict_key(K) will also return K.
However, the clashes are for unusual containers with a type as the first
element, instead of "usual" containers containing lists, tuples, strings,
etc. Unless you deal with tuples with the first item being a type, you
shouldn't come across any clashes.
Also: nice work on supporting recursive data structures, thanks.
--
Steven.
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