Op 2005-01-14, Steve Holden schreef <[EMAIL PROTECTED]>: > Antoon Pardon wrote: > >> Op 2005-01-14, Peter Maas schreef <[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. >>> >> >> I had a look and I think you should correct the followingr: >> >> Dictionary lookup with mutable types like lists is a source of >> unpleasant surprises for the programmer and therefore impossible in >> Python. >> > Better, perhaps, to say: > > Dictionary lookup with mutable types like lists can be a > source of unpleasant surprises for the programmer and > therefore not recommended in Python.
IOW Python discourages mutable types in any type of container. >> It is not impossible in Python. It may be discouraged but it is not >> impossible since I have already done so. >> > If I discouraged you from shooting yourself in the foot would you do > that too? If I chose not to shoot my self in the foot, it wouldn't be because you discouraged me. It would be because I heard good arguments. What are good arguments or bad and how much weight they have depends on the person and on the circumstances. So a simple rule like: Never use a mutable as a key in a dictionary will sometimes not be the best solution. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
