Add # LuL to every file recursively

[
    (lambda text: open(file, 'w').write(text))('# LuL\n' + open(file).read())
    for (dirpath, dirnames, filenames) in __import__('os').walk(".")
    for file in
        [__import__('os').path.join(dirpath, f) for f in filenames]
]