A task I actually ran into at work this week: get a filtered list of subdirectories, exclude some based on a list of names to be ignored, sort the remainder by their modification times. (This problem was actually also the origin of my recent filter_walk recipe: http://code.activestate.com/recipes/577913-selective-directory-walking/) Translated to 3.x (i.e. the generator's .next() method is replaced by the next() builtin), the code would look roughly like this: # Generate list of candidate directories sorted by modification time candidates = next(filter_walk(base_dir, dir_pattern=dir_filter, depth=0)).subdirs candidates = (subdir for subdir in candidates if not any(d in subdir for d in dirs_to_ignore)) def get_mtime(path): stat_path = os.path.join(base_dir, path) return os.stat(stat_path).st_mtime candidates = sorted(candidates, key=get_mtime) Now, that could theoretically be split out to a separate function (passing base_dir, dir_filter and dirs_to_ignore as arguments), but the details are going to vary too much from use case to use case to make reusing it practical. Even factoring out "get_mtime" would be a waste, since you end up with a combinatorial explosion of functions if you try to do things like that (it's the local code base equivalent of "not every 3 line function needs to be in the standard library"). I can (and do) use vertical white space to give some indication that the calculation is complete, but PEP 3150 would allow me to be even more explicit by indenting every step in the calculation except the last one: candidate_dirs = sorted(candidate_dirs, key=get_mtime) given: candidate_dirs = next(filter_walk(base_dir, dir_pattern=dir_filter, depth=0)).subdirs candidate_dirs = (subdir for subdir in candidates if not any(d in subdir for d in dirs_to_ignore)) def get_mtime(path): stat_path = os.path.join(base_dir, path) return os.stat(stat_path).st_mtime Notice how the comment from the original version becomes redundant in the second version? It's just repeating what the actual header line right below it says, so I got rid of it. In the original version it was necessary because there was no indentation in the code to indicate that this was all just different stages of one internal calculation leading up to that final step to create the sorted list. Cheers, Nick. -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia