def replace(line_val, seq):
    """
    Replace special characters
    :param line_val: line as string
    :param seq: sequence number
    :return: changed value
    """
    # replace TAB to ','
    rtn = line_val.replace('\t', ',')
    # remove line break
    rtn = rtn.replace('\r\n', '')
    rtn = rtn.replace('\n', '')
    rtn = rtn.replace('NULL', '0')
    # verify if there is a 'NULL' or 'ZZ' row
    _tmp_lst = rtn.split(',')
    for _tmp in _tmp_lst:
        _tmp = _tmp.strip().upper()
        if 'ZZ' == _tmp:
            rtn = None
            break

    if rtn is not None:
        _tmp_lst.append(str(seq))
        rtn = ','.join(_tmp_lst)
        rtn = rtn + '\n'

    return rtn