def split_part_numbers(row):
    """Split part number string into main and alternates."""
    
    part_no = ''
    part_no_alt = ''

    if row['manuf part'] != '':
        tmp = row['manuf part'].split(None, 1)
        part_no = tmp[0]
        if len(tmp) > 1:
            part_no_alt = tmp[1]
    row['manuf part'] = part_no
    row['manuf part alt'] = part_no_alt
            
    return row