Script to explore the use of different types of sort keys, including "natural sort order"

sorting.py

# Compare effects of using different sort keys

import os
import locale
import re

class SortKeys:
    natural_sort_digits = re.compile(r'(\d+)')
    @classmethod
    def default(self,filename):
        # Default Python ordering for sort
        return filename
    @classmethod
    def locale(self,filename):
        # Ordering using the locale
        return locale.strxfrm(filename)
    @classmethod
    def natural(self,filename):
        # Natural order sorting from Pavel Repin, see
        # http://stackoverflow.com/a/5997173/579925
        return tuple(int(token) if match else token
                     for token, match in
                     ((fragment, self.natural_sort_digits.search(fragment))
                      for fragment in self.natural_sort_digits.split(filename)))

def list_files(dirn,sort_key=None):
    # Print a list of all files under a directory
    files = []
    for d in os.walk(dirn):
        for f in d[2]: 
            files.append(os.path.join(str(d[0])[len(dirn):].lstrip(os.sep),f))
    files.sort(key=sort_key)
    for f in files:
        print f
    return files

if __name__ == "__main__":
    print "# Default ordering"
    default_order = list_files('.',sort_key=SortKeys.default)
    print "# Locale ordering"
    locale_order = list_files('.',sort_key=SortKeys.locale)
    print "# Natural ordering"
    natural_order = list_files('.',sort_key=SortKeys.natural)
    print "Default == locale:\t%s" % (locale_order == default_order)
    print "Default == natural:\t%s" % (natural_order == default_order)