对数据库 Python 进行循环输入时出现异常答案

【问题标题】：got exception when do a loop input to database Python对数据库 Python 进行循环输入时出现异常
【发布时间】：2018-01-30 05:00:31
【问题描述】：

所以，我想以自动增量作为主键多次输入数据，并将主键作为输入结果返回。这是我的代码：

connectDB.py

import pymysql
class auth:

   db = pymysql.connect("localhost","root","","rfid")

   cursor = db.cursor()

   def inputData(nama):
       sql = "INSERT INTO auth (nama) VALUES ('%s');" % (nama)

       try:
           auth.cursor.execute(sql)
           auth.db.commit()


           result = auth.cursor.lastrowid

           auth.db.close()

           return result
       except:
           err = "Error: unable to fetch data"
           auth.db.rollback()

           auth.db.close()

           return err

test.py

import re
import PyMySQL
from connectDB import auth

while True:

     inputs2 = input("masukan nama: ")


     hasil = auth.inputData(inputs2)

     print(hasil)

所以，当我第一次输入时是成功的，但是当我再次输入时，我得到了一个错误异常：

Traceback (most recent call last):
  File "/home/pi/Desktop/learn/RFIDdatabase/connectDB.py", line 29, in inputData
auth.cursor.execute(sql)

  File "/usr/local/lib/python3.4/dist-packages/pymysql/cursors.py", line 166, in execute
result = self._query(query)

  File "/usr/local/lib/python3.4/dist-packages/pymysql/cursors.py", line 322, in _query
conn.query(q)

  File "/usr/local/lib/python3.4/dist-packages/pymysql/connections.py", line 855, in query
self._execute_command(COMMAND.COM_QUERY, sql)

  File "/usr/local/lib/python3.4/dist-packages/pymysql/connections.py", line 1071, in _execute_command
raise err.InterfaceError("(0, '')") 
pymysql.err.InterfaceError: (0, '')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test.py", line 12, in <module>
hasil = auth.inputData(inputs2)

  File "/home/pi/Desktop/learn/RFIDdatabase/connectDB.py", line 41, in inputData
auth.db.rollback()

  File "/usr/local/lib/python3.4/dist-packages/pymysql/connections.py", line 792, in rollback
self._execute_command(COMMAND.COM_QUERY, "ROLLBACK")

  File "/usr/local/lib/python3.4/dist-packages/pymysql/connections.py", line 1071, in _execute_command
raise err.InterfaceError("(0, '')")
pymysql.err.InterfaceError: (0, '')

那么，异常原因是什么？

【问题讨论】：

标签： python python-3.x pymysql

【解决方案1】：

当然你会得到一个异常 - 因为你在执行查询后关闭连接：

auth.cursor.execute(sql)
auth.db.commit()

result = auth.cursor.lastrowid

auth.db.close()  # < HERE

return result

您可能会得到一个“关闭游标上的操作”异常，该异常由您过于宽泛的裸 except 子句 (which is bad) 处理 - 然后 - 回滚在 auth.db.rollback() 启动，失败并没有描述性和可以理解的错误。

其他问题：

我会使用 db 和 cursor 实例变量而不是类变量 (differences)
不要“字符串格式”你的查询 - proper parameterize them

【讨论】：