Re: proposed proposal: set.values()
Fredrik Lundh [EMAIL PROTECTED] writes: Nobody says you shouldn't use list(s) if you know you're dealing with a set. The idea of s.values() is so you can duck-type between dicts and sets. if y is a dict, x in y looks for a matching key, not for a matching value. Good point, the duck typing mismatches on x in y and there's nothing that can be done about that. Imagine a Bag (multiset) object; it can have multiple occurrences of a single value. A keys() operation on it should return unique items, but values() should return the multiple occurrences. -- http://mail.python.org/mailman/listinfo/python-list
Re: proposed proposal: set.values()
Terry Reedy [EMAIL PROTECTED] writes: 1. It is pure duplication that *adds* keystrokes. Nobody says you shouldn't use list(s) if you know you're dealing with a set. The idea of s.values() is so you can duck-type between dicts and sets. 2. It copies the wrong aspect of dict. A set is like dict.keys (no duplicates, hashable), not dict.values (duplicates and non-hashables ok). I'd say keys is incorrect, since sets don't have keys: import sets s=sets.Set((1,2,3)) s[1] Traceback (most recent call last): File stdin, line 1, in ? TypeError: unindexable object I don't think it's important that some values that can occur in dicts (e.g. non-hashables) can't occur in sets. There are similarly values for complex numbers that can't be expressed as floats, but that doesn't mean __add__ shouldn't work on both. 3. It copies a workaround. Conceptually, dict.keys() and dict.items() should each be a set, not list, and would have been if Python had had sets at birth. Dict.values() should be a multiset or bag. The order of any is purely artificial and random. Set.keys() or set.values() should be the set itself. I guess it's ok if sets.items() is the same as sets.values(). Sets don't have keys. dict.values() is what it is for historical reasons as you state, and would be hard to change, so it makes sense for set.values() to work the same way. 4. The workaround will change or even better go away. In 3.0, ,keys, .values and .items not be lists. The initial proposal was to replace them with iterators (the current iterkeys, etc). A current proposal (still in development) is for an iterable set- or multiset-like view on the underlying dict. I hadn't heard of this but it does make some sense. However, sets.values (and maybe sets.items) should be treated the same way, under my proposed proposal. -- http://mail.python.org/mailman/listinfo/python-list
Re: proposed proposal: set.values()
Paul Rubin wrote: Terry Reedy [EMAIL PROTECTED] writes: 1. It is pure duplication that *adds* keystrokes. Nobody says you shouldn't use list(s) if you know you're dealing with a set. The idea of s.values() is so you can duck-type between dicts and sets. You could just do the following... class vset(set): ... values = set.copy ... s = vset([1,2,3]) s.values() vset([1, 2, 3]) for x in s.values(): ... x ... 1 2 3 Cheers, Ron -- http://mail.python.org/mailman/listinfo/python-list
proposed proposal: set.values()
I'm thinking of proposing that a values method be added to set objects, analogously with dicts. If x is a set, x.values() would be the same as list(x). This feels logical, and it would allow unified treatment of dicts and sets in some contexts. Any objections? -- http://mail.python.org/mailman/listinfo/python-list
Re: proposed proposal: set.values()
Paul Rubin http://phr.cx@NOSPAM.invalid wrote in message news:[EMAIL PROTECTED] I'm thinking of proposing that a values method be added to set objects, analogously with dicts. If x is a set, x.values() would be the same as list(x). This feels logical, and it would allow unified treatment of dicts and sets in some contexts. Any objections? 1. It is pure duplication that *adds* keystrokes. 2. It copies the wrong aspect of dict. A set is like dict.keys (no duplicates, hashable), not dict.values (duplicates and non-hashables ok). 3. It copies a workaround. Conceptually, dict.keys() and dict.items() should each be a set, not list, and would have been if Python had had sets at birth. Dict.values() should be a multiset or bag. The order of any is purely artificial and random. Set.keys() or set.values() should be the set itself. 4. The workaround will change or even better go away. In 3.0, ,keys, .values and .items not be lists. The initial proposal was to replace them with iterators (the current iterkeys, etc). A current proposal (still in development) is for an iterable set- or multiset-like view on the underlying dict. Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: proposed proposal: set.values()
Terry Reedy [EMAIL PROTECTED] writes: 1. It is pure duplication that *adds* keystrokes. Nobody says you shouldn't use list(s) if you know you're dealing with a set. The idea of s.values() is so you can duck-type between dicts and sets. 2. It copies the wrong aspect of dict. A set is like dict.keys (no duplicates, hashable), not dict.values (duplicates and non-hashables ok). I'd say keys is incorrect, since sets don't have keys: import sets s=sets.Set((1,2,3)) s[1] Traceback (most recent call last): File stdin, line 1, in ? TypeError: unindexable object I don't think it's important that some values that can occur in dicts (e.g. non-hashables) can't occur in sets. There are similarly values for complex numbers that can't be expressed as floats, but that doesn't mean __add__ shouldn't work on both. 3. It copies a workaround. Conceptually, dict.keys() and dict.items() should each be a set, not list, and would have been if Python had had sets at birth. Dict.values() should be a multiset or bag. The order of any is purely artificial and random. Set.keys() or set.values() should be the set itself. I guess it's ok if sets.items() is the same as sets.values(). Sets don't have keys. dict.values() is what it is for historical reasons as you state, and would be hard to change, so it makes sense for set.values() to work the same way. 4. The workaround will change or even better go away. In 3.0, ,keys, .values and .items not be lists. The initial proposal was to replace them with iterators (the current iterkeys, etc). A current proposal (still in development) is for an iterable set- or multiset-like view on the underlying dict. I hadn't heard of this but it does make some sense. However, sets.values (and maybe sets.items) should be treated the same way, under my proposed proposal. -- http://mail.python.org/mailman/listinfo/python-list
Re: proposed proposal: set.values()
Paul Rubin wrote: 1. It is pure duplication that *adds* keystrokes. Nobody says you shouldn't use list(s) if you know you're dealing with a set. The idea of s.values() is so you can duck-type between dicts and sets. if y is a dict, x in y looks for a matching key, not for a matching value. /F -- http://mail.python.org/mailman/listinfo/python-list
