def expand_NDIG(w):
    """Expand digit sequences to a series of words."""
    try:
        numbers = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']
        num_words = ['zero', 'one', 'two', 'three', 'four', 'five', 'six',
            'seven', 'eight', 'nine']
        str2 = ''
        for n in w:
            if n.isdigit():
                str2 += num_words[numbers.index(n)]
                str2 += ' '
            elif n == '.':
                str2 += 'dot'
                str2 += ' '
            else:
                str2 += ''
        return str2[:-1]
    except (KeyboardInterrupt, SystemExit):
        raise
    except:
        return w
