def write_vocab(vocab, filename):
    """Writes a vocab to a file

    Writes one word per line.

    Args:
        vocab: iterable that yields word
        filename: path to vocab file

    Returns:
        write a word per line

    """
    print('Writing vocab...')
    with open(filename, 'w') as f:
        for i, word in enumerate(vocab):
            if i != len(vocab) - 1:
                f.write('{}\n'.format(word))
            else:
                f.write(word)
    print('- done. {} tokens'.format(len(vocab)))
