解决办法：datetime.datetime(2018, 10, 30, 14, 9, 0, 669000, tzinfo=tzlocal()) is not JSON serializable

import pymssql
import json



def conn():
    connect = pymssql.connect('192.168.28.38:1433', 'root', '123456', 'test')
    if connect:
        #print("sucessful")
        cur = connect.cursor(as_dict=True)  # 若as_dict为False 返回的是一个列表，而不是字典。
        sql = "select * from tb_name "
        cur.execute(sql)
        ret = cur.fetchall() # ret 中包含datetime.datetime(2018, 10, 30, 14, 9, 0) 
        connect.close()
        ret_json = json.dumps(ret, default=str)
        return ret_json


if __name__ == '__main__':
    conn = conn()
    #print(type(conn))
    print(conn)