Traverse Files and Rename

from os import listdir, rename
from os.path import isfile, join

#path = '/Volumes/HD-PATU3/Pawel/Pictures'
path = './'

for f in listdir(path):
    if not isfile(join(path, f)):
        spl = f.split('_')
        #print 'File: %s' % f
        if spl[0].__len__() == 2:
            newf = '20%s' % f
            print 'New File: %s' % newf
            rename(join(path, f), join(path, newf))
            #for part in spl:
            #print 'Part: %s' % part