[基本上，我试图做一个python-sql连接器程序，但此刻我被这个错误困住了

Question

我收到错误->

Traceback (most recent call last):
  File "C:\Users\REJI\Desktop\project\the project\book_store.py", line 346, in <module>
    sale()
  File "C:\Users\REJI\Desktop\project\the project\book_store.py", line 321, in sale
    read_sale()
  File "C:\Users\REJI\Desktop\project\the project\book_store.py", line 217, in read_sale
    print(body%(str(row[0]),row[4][0:20],str(row[2])[0:15],str(row[1]),str(row[3])))
TypeError: 'NoneType' object is not subscriptable

对于此python->

def read_sale():
    qs='''select s1.*,book_title from sale s1, bookmaster b1
where s1.book_no=b1.book_no order by s1.book_no'''
    cur.execute(qs)
    data=cur.fetchall()
    head='''\
               All Sales
+-------+--------------------+------------+----------+----------+
|Book No|       Title        |Date of sale| Quantity |   Price  |
+-------+--------------------+------------+----------+----------+'''
    body='''\
|%7s|%20s|%12s|%10s|%10s|
+-------+--------------------+------------+----------+----------+'''
    print(head)
    for row in data:
        print(body%(str(row[0]),str(row[4])[0:20],str(row[2])[0:15],str(row[1]),str(row[3])))

并且用于在此mysql表中的列中输入值->

| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| book_no  | int(30)     | YES  |     | NULL    |       |
| quantity | varchar(15) | YES  |     | NULL    |       |
| sdate    | date        | YES  |     | NULL    |       |
| price    | int(40)     | YES  |     | NULL    |       |
| title    | varchar(20) | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+

并且如果我将某些代码更改为str，我得到以下结果，我不希望列标题和数量的信息不显示任何信息，我希望它们显示mysql表中存在的某个值。] >

Enter your choice 1-51
               All Sales
    +-------+--------------------+------------+----------+----------+
    |Book No|       Title        |Date of sale| Quantity |   Price  |
    +-------+--------------------+------------+----------+----------+
    |    147|          **None**  |  2019-11-20|  **None**|        50|
    +-------+--------------------+------------+----------+----------+
    sale Menu`enter code here`
            -----------------
            1.To read_sale
            2.To add_sale
            3.TO Exit and return to main menu 
因此，如果可以的话，请帮助我，对你的帮助表示感谢谢谢

我收到错误->追溯（最近一次通话）：文件“ C：\ Users \ REJI \ Desktop \ project \ theproject \ book_store.py”，行346，位于[[sale（）文件中：\ Users \ REJI \ Desktop \ project \ ...

Answer 1

[您的某些书显然有title = NULL，有些销售有quantity = NULL。您需要先检查这些内容，然后再尝试格式化它们。