基本上，我正在尝试编写一个python-sql连接器程序，但是现在我遇到了这个错误

Question

我得到了错误-->

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

对于这个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])))

用于将值输入到此mysql表中存在的列中-->

| 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    |       |
+----------+-------------+------+-----+---------+-------+

如果我将一些代码改为str，我会得到下面的结果，我不希望title和quantity列的信息显示为none，我希望它们显示存在于mysql表中的某个值。

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 

如果您能帮助我，我们将不胜感激，谢谢！

Answer 1

显然，你的一些书有title = NULL，有些销售有quantity = NULL。在尝试格式化它们之前，您需要检查它们。

for row in data:
    if row[4] is None:
        row[4] = 'Untitled'
    if row[2] is None:
        row[2] = 0
    print(body%(str(row[0]),row[4][0:20],str(row[2])[0:15],str(row[1]),str(row[3])))

顺便说一句，由于您使用的是字符串格式，您可以简单地在数字数据的格式字符串中使用%d，而不是在参数列表中调用str()。