On 2006-07-14, Nick Vatamaniuc <[EMAIL PROTECTED]> wrote: >>I have a tree class, a tree acts like a dictionary, but when you >> iterate over it, it always iterates over the keys in order. > > Antoon, > > First of all there is a distinction between ordered and un-ordered data > types. You can only slice ordered data types. Lists and tuples are > ordered while the keyset (note the _set_ part) of a dictionary is a set > - it is un-ordered and consists of unique elements, the keys.
That doesn't has to be. Let as talk about a mapping. A mapping is a way to associate a key with a value. Now one way to implement a mapping is a hash table, this is how python dictionaries are implemented. Now I have an other mapping implementation, look at: http://www.pardon-sleeuwaegen.be/antoon/avltree.html Now this mapping type has as a property that the order of the keys is somehow stored with it, so that each time you call the keys, values, or items methods, you will get a list according the order of the keys. (The same goes for the itervariants). > Besides, I don't really understand what you mean by saying "a tree acts > like a dictionary"? You don't really iterate over the dictionary > because the keys are not in order! Remeber that. The confusing part is > that ks=dic.keys() will return a list so that makes you think ks[0] is > somehow first for some reason, but it shouldn't be. My module is implemented to have that property. It is called a tree because the implementation is a tree. May be with the API provided you think a tree is not a good name for this class and you may have a point there, but that is not what this discussion is about. > You see, dictionaries were there in Python before sets(), that is why > when sets are supposed to be used a dictionary or list is used. keys() > is one of these example. Hopefully this will change in P3K so that the > key_set_ of a dictionary is a set() so people don't get confused. And what do you think should be the result of keys of my Tree class? -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
