"Peter Maas" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
I have summarized the discussion about the usability of lists (and and other mutable types) as dictionary keys and put it into the Python wiki.URL: http://www.python.org/moin/DictionaryKeys.
This summary might be used as a reference should the 'mutable dictionary keys' issue come up again in c.l.py.
The last piece has an incorrect conclusion. Lists are not safe _because_ the cmp function is NOT a compare of id(list), but is based on list contents, which can change at any time.
It should also be emphasized that the default instance hash and cmp functions quoted make it impossible for two different instances to compare equal, thus there is no reason to store them as dictionary keys: it's simpler to make the value an attribute of the instance and bypass the additional complexity of the dictionary.
John Roth
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