如何在Python中为MySQL设置空值

这是我的SQL命令行版本。

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 122
Server version: 5.0.95 Source distribution

+---------------+-------------+------+-----+---------+-------+
| Field         | Type        | Null | Key | Default | Extra |
+---------------+-------------+------+-----+---------+-------+
| Action        | char(1)     | NO   |     | R       |       | 
| EndpointId    | int(11)     | NO   | MUL | NULL    |       | 
| DeviceType    | smallint(6) | NO   |     | NULL    |       | 
| ChannelNumber | smallint(6) | NO   |     | 0       |       | 
| ActionDate    | date        | YES  |     | NULL    |       | 
| InsertDate    | date        | YES  |     | NULL    |       | 
+---------------+-------------+------+-----+---------+-------+

sql_cmd = \
                """insert into cs_remove
                (
                Action, EndpointId, DeviceType, ChannelNumber, ActionDate, InsertDate
                )
                VALUES 
                (
                %s, %s, %s, %s, %s, %s
                )
                """

            print(base_date)
            sql_data = ('R', ept_id, ept_type, ept_ch, "NULL", base_date);

该示例最后将0000-00-00放入日期字符串。我想要空值。我可以从mysql命令行执行此操作,但不能从Python执行。任何帮助都将不胜感激。