Raymond Hettinger <[EMAIL PROTECTED]> writes: > I think the OP would have been better-off with plain > vanilla Python such as: > > See http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/259173
But that recipe generates the groups in a random order depending on the dict hashing, instead of keeping them in the original sequence's order, which the OP's application might well require. itertools.groupby really is the right thing. I agree that itertools is not the easiest module in the world for beginning programmers to understand, but every serious Python user should spend some time figuring it out sooner or later. Iterators and itertools really turn Python into a higher-level language than it was before, giving powerful and streamlined general-purpose mechanisms that replace a lot of special-purpose hand-coding that usually ends up being a lot more work to debug in addition to bloating the user's code. Itertools should by no means be thought of as just a performance hack. It makes programs smaller and sharper. It quickly becomes the One Obvious Way To Do It. In my past few kloc of Python, I think I've written just one or two "class" statements. I used to use class instances all the time, to maintain little bits of state that had to be held between different operations in a program. Using itertools means I now tend to organize entire programs as iterator pipelines so that all the data runs "through the goose" exactly once and there is almost no need to maintain any state anywhere outside the scope of simple function invocations. There are just fewer user-written moving parts when a program is written that way, and therefore fewer ways for the program to go wrong. Messy edge cases that used to take a lot of thought to handle correctly now need no attention at all--they just handle themselves. Also I think it's generally better to use a documented standard library routine than a purpose-written routine or even a downloaded recipe, since the stdlib routine will stay easily available from one project to another and as the user gains experience with it, it will become more and more powerful in his or her hands. Also, these days I think I'd write that recipe with a defaultdict instead of setdefault, but that's new with Python 2.5. -- http://mail.python.org/mailman/listinfo/python-list
