def get_stock_exchange(stock_code: str) -> str:
    """
    Get the stock market according to the code rule.
    :param stock_code: The stock code that need to check/
    :return: Exchange. SSE - Shanghai, SZSE - Shenzhen. Empty string if not recognized.
    """
    if len(stock_code) != 6:
        return ''
    if stock_code.startswith('000') or stock_code.startswith('300') \
            or stock_code.startswith('200')or stock_code.startswith('002'):
        # 000: 普通
        # 300: 创业板
        # 200: B股
        # 002: 中小板
        return 'SZSE'
    if stock_code.startswith('60') or stock_code.startswith('688') or stock_code.startswith('900'):
        # 600, 601, 603: 普通
        # 688: 科创板
        # 900: B股
        return 'SSE'
    return ''