On Sun, Nov 16, 2008 at 7:15 PM, Arnaud Delobelle <[EMAIL PROTECTED]> wrote: > Mr.SpOOn <[EMAIL PROTECTED]> writes: > >> Hi, >> I'm trying to create a class which inherit a list to change some behavior. >> This list should contain other instance objects and has to manage >> these instances in a particular way. >> >> 1) I need to sort this elements in this list, but they must be sorted >> using an instance variable. > > I don't understand what this means.
Well, inside the elements I need to order there is a variable that stores a numeric value. I need to sort the elements using this value. > Or sort them according to a key. Ok, knowing what to search for I cleared my ideas. I think I just have to choose between redefining __cmp__() or using the key argument. >> 2) I need to have just unique elements. Maybe this is related to first >> question (or maybe not). Again, to estabilish the uniqueness of an >> element I have to use an instance variable. I think I have to rewrite >> both the methods append() and __contains__(), but I'm not sure how. >> >> For the first one I did: >> >> def append(self, element): >> if element in self: >> pass >> else: >> list.append(self, element) >> >> It seems right to me, but I have no idea what to do with __contains__() > > Why do you need to redefine __contains__? Well, to check the presence of an element according to an attribute. > If I were you, I wouldn't inherit from list because it seems that your > list-like object quite different from a plain list. The most obvious choice seems to be stes. But the order is really important. Maybe the best solution is using sets and convert them to list when I need to access them in the correct order. >You should probably use the `bisect` module >(http://docs.python.org/library/bisect.html) for searching and >inserting into the list as it takes advantage of and ensures that the >list keeps sorted. It also means that __contains__ and some other >operations become O(log N) rather than O(N). This seems good too, but I'd always have to check the presence of an element before inserting a new one and it's still not clear to me how to do it. Thanks everybody. -- http://mail.python.org/mailman/listinfo/python-list
