Walk from a directory (up or down) yielding the results of the passed function.

walk_dates.py

import os

dir = "blog"

# Walk from a dir returning the results of function.
# The path below the dir should be set out in date format.
# path example: /YYYY/MM/DD/file.ext
# path example: /2012/01/30/file.txt
def walk_dates_and_apply( dir, function, desc ):
    for walking in os.walk( dir, topdown = desc ):
        walking[ 1 ].sort( reverse = desc )
        for result in function( *walking, desc = desc ):
            yield result

# Example function for returning latest/'up to date' files.
def newest_files( dirname, dirnames, filenames, desc = True ):
    paths = [ os.path.join( dirname, x ) for x in filenames ]
    t = os.path.getmtime
    paths.sort( reverse = desc, cmp = lambda x,y: int( t( x ) - t( y ) ) )
    for file in paths:
        yield file 

if __name__ == "__main__":
    # Print out all of the file paths, newest to oldest.
    for f in walk_dates_and_apply( dir, newest_files, True ):
        print f