python 数据库请求未更新

Question

我在 python 脚本中从数据库中提取数据，该脚本在启动时有效，但在我更改数据库中的值时不会更新。

脚本最初连接到数据库然后选择id等于1的所有内容（这有一些我打算使用的列）

然后用 garage 列中的内容更新全局变量 garageHeating，假设它在启动时等于 0。

while 循环打印出这个变量，该变量在开始时将为 0

如果我将数据库中的列车库更改为 10，python 脚本将保持为 0。它不会更新我认为应该执行的全局变量

下面是我的剧本

import mysql.connector as mariadb

mariadb_connection = mariadb.connect(
  host="localhost",
  user="garage",
  passwd="*******",
  database="mydb"
  )
cursor = mariadb_connection.cursor()

garageHeating = 0 

def readDbHeating():
   global garageHeating
   result = []
   try:
      cursor.execute ("SELECT * FROM heating WHERE id = '1'")
      for reading in cursor.fetchall():
         result.append (reading)
         garageHeating = result[0][8]
   except () as e:
      print (e)

while 1:
   readDbHeating()
   print garageHeating

我已经编辑了下面显示的上面的代码，以在函数外部显示全局变量，并在 try 命令中打印出结果。在第一次从数据库中提取数据后，我仍然遇到同样的问题，脚本继续显示第一组数据，但如果我更改数据库记录，则不会更新到新数据。

import mysql.connector as mariadb

mariadb_connection = mariadb.connect(
  host="localhost",
  user="garage",
  passwd="14Odiham",
  database="mydb"
  )
cursor = mariadb_connection.cursor()

global garageHeating

def readDbHeating():
   result = []
   try:
      cursor.execute ("SELECT * FROM heating WHERE id = '1'")
      for reading in cursor.fetchall():
         result.append (reading)
         garageHeating = result[0][8]
         print garageHeating
         print result
   except () as e:
      print (e)

while 1:
    readDbHeating()
    #print garageHeating

Answer 1

我好像可以用了。我必须打开数据库连接，然后关闭函数内的连接，如下所示。这与我过去使用 mysql 所做的不同，但目前至少可以使用

import mysql.connector as mariadb
import time

garageHeating = 0

def readDbHeating():
   mariadb_connection = mariadb.connect(
     host="localhost",
     user="garage",
     passwd="14Odiham",
     database="mydb"
     )
   cursor = mariadb_connection.cursor()
   result = []
   try:
      cursor.execute ("SELECT * FROM heating WHERE id = '1'")
      for reading in cursor.fetchall():
         result.append (reading)
   except () as e:
      print (e)
   finally:
    #closing database connection.
    if(mariadb_connection.is_connected()):
        mariadb_connection.close()
        print("connection is closed")
   return (result)


while 1:
   test = readDbHeating()
   print test
   time.sleep(1)

Answer 2

您必须在执行查询之前调用 MySQLdb.connections.Connection.commit 或在连接对象上设置 autocommit。

查询前提交

def readDbHeating():
   global garageHeating
   result = []
   try:
      # commit
      mariadb_connection.commit()
      cursor.execute ("SELECT * FROM heating WHERE id = '1'")
      for reading in cursor.fetchall():
         result.append (reading)
         garageHeating = result[0][8]
   except () as e:
      print (e)

创建连接时自动提交

mariadb_connection = mariadb.connect(
  host="localhost",
  user="garage",
  passwd="14Odiham",
  database="mydb",
  # Auto commit
  autocommit=True
  )

连接创建后自动提交

mariadb_connection.autocommit(True)

python 数据库请求未更新

python database request not updating

python

mariadb

mariadb-connect-engine