def save(f, arr, vocab):
    """
    Save word embedding file.

    Args:
        f (File): File to write the vectors. File should be open for writing
            ascii.
        arr (numpy.array): Numpy array with ``float`` dtype.
        vocab (iterable): Each element is pair of a word (``bytes``) and ``arr``
            index (``int``). Word should be encoded to str apriori.
    """
    itr = iter(vocab)
    # Avoid empty line at the end
    word, idx = next(itr)
    _write_line(f, arr[idx], word)
    for word, idx in itr:
        f.write(b'\n')
        _write_line(f, arr[idx], word)