def GetFileMd5(filename):

    if not os.path.isfile(filename):

        return

    myhash = hashlib.md5()

    f = file(filename,'rb')

    while True:

        b = f.read(8096)

        if not b :

            break

        myhash.update(b)

    f.close()

    return myhash.hexdigest()