Python/Linux: Create .md5 files for every file in a directory and it's subdirectories

generate_md5.py

import os
import subprocess

ignored_extensions = ('.py', '.md5')

rootdir = os.getcwd()
for subdir, dirs, files in os.walk(os.getcwd()):
    for filename in files:
        os.chdir(subdir)
        relative_path = os.path.normpath(os.path.relpath(os.getcwd(), rootdir))
        relative_filename = os.path.join(relative_path, filename)

        if os.path.isfile(filename+'.md5'):
            print "EXISTS: %s.md5" % relative_filename
            
        elif not filename.endswith(ignored_extensions):
            with open(filename+'.md5',"wb") as md5:
                subprocess.Popen(["md5sum", filename], stdout=md5)
                print "CREATE: %s.md5" % relative_filename