[Tutor] quicksort using list comprehension
I'm trying to program quicksort using list comprehension. The following gives me a type mismatch error for +. def qsort (t): if len (t) 1: return qsort([x for x in t[1:] if x = t[0]]) + [t[0]] + qsort([x for x in t[1:] if x t[0]]) I know this sounds strange but I have and idea it (or something similar) worked when I last tried Python a yr or so ago. An earlier version of Python? Logesh Pillay ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] quicksort using list comprehension
I think you have to return a value when len(t) = 1. You don't return anything which means you return None which can't be added to a list. Kent Logesh Pillay wrote: I'm trying to program quicksort using list comprehension. The following gives me a type mismatch error for +. def qsort (t): if len (t) 1: return qsort([x for x in t[1:] if x = t[0]]) + [t[0]] + qsort([x for x in t[1:] if x t[0]]) I know this sounds strange but I have and idea it (or something similar) worked when I last tried Python a yr or so ago. An earlier version of Python? Logesh Pillay ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] quicksort using list comprehension
On Apr 9, 2005, at 21:50, Kent Johnson wrote: I think you have to return a value when len(t) = 1. You don't return anything which means you return None which can't be added to a list. Kent Yup. Here's a quicksort I did, adapting an example from the Wikipedia article on Haskell: def qsort(toSort): if toSort == []: return [] else: x = toSort[0] elts_lt_x = [y for y in toSort if y x] elts_gt_x = [y for y in toSort if y x] return qsort(elts_lt_x) + [x] + qsort(elts_gt_x) It is, of course, nowhere near as optimal as a real quicksort algorithm (like the one the list.sort method implements). -- Max maxnoel_fr at yahoo dot fr -- ICQ #85274019 Look at you hacker... A pathetic creature of meat and bone, panting and sweating as you run through my corridors... How can you challenge a perfect, immortal machine? ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
