On Sat, Nov 6, 2010 at 10:43 PM, not1xor1 (Alessandro) <" "@libero.it> wrote: > Hi, > > I'd like to know what is the best way to subclass str > I need to add some new methods and that each method (both new and str ones) > return my new type > > For instance I've seen I can do: > > class mystr(str): > > def between(self, start, end): > i = self.index(start) + len(start) > j = self.index(end, i) + len(end) > return self[i:j], self[j:] > > def replace(self, old, new='', count=-1): > return mystr(str.replace(self, old, new, count)) > <snip> > I wonder if I have to redefine all methods one by one or if there is a sort > of hook to intercept all methods calls and just change the return type
You could subclass UserString instead of str; all of UserString's methods seem to ensure that instances of the subclass rather than just plain strs or UserStrings are returned. See http://docs.python.org/library/userdict.html#UserString.UserString But you should also consider whether your additions absolutely *must* be methods. Merely instead defining some functions that take strings as parameters is obviously a simpler, and probably more performant, approach. If you insist on subclassing str, there's no such hook; you'll have to override all the methods yourself.* Cheers, Chris -- *Well, you could override only the __special__ methods and __getattribute__(), or use metaprogramming, but at that point you might as well go the UserString route if possible. http://blog.rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
