在QMessageBox中显示MySQL错误

时间:2012-09-14 17:36:02

标签: python mysql error-handling pyqt qmessagebox

我正在运行一个本地MySQL服务器来开发我的PyQt应用程序。如果我可以在服务器关闭的情况下显示QMessageBox会很好,这样最终用户就会知道为什么应用程序无法启动。

如果我关闭服务器并从终端运行我的程序,我得到通常的回复:

pymysql.err.OperationalError: (2003, "Can't connect to MySQL server on '127.0.0.1' (2)")

我的代码很简单

import pymysql as lite

con = lite.connect(host='127.0.0.1',unix_socket='/run/mysqld/mysqld.sock', user='ivica',passwd='pass',db='baza',charset='utf8')

#define one class that inherits QMainWindow and so on...

有没有办法让我真正显示一个QMessageBox,说明“MySQL服务器已关闭!”或类似的东西?如果MySQL服务器没有运行,我的应用程序窗口甚至都不显示,只是终端错误。

:编辑:

建议更改后,我的代码如下所示:

con = None #this is how I make it global, eg. not in any method or class (?)

def dbconnect():
    global con
    #con = None
    try:
        if os.name == 'nt':
            con = lite.connect(host='127.0.0.1', user='ivica',passwd='pass',db='baza',charset='utf8')
        else:
            con = lite.connect(host='127.0.0.1',unix_socket='/run/mysqld/mysqld.sock', user='ivica',passwd='pass',db='baza',charset='utf8')
    except lite.err.OperationalError as err:
        msgBox = QtGui.QMessageBox()
        msgBox.setText(str(err))
        msgBox.show()
    return con

class Logon(QtGui.QDialog):
    def __init__(self):
        QtGui.QDialog.__init__(self)
        self.ui=Ui_dlgLogovanje()
        self.ui.setupUi(self)
        QtCore.QObject.connect(self.ui.dugmeUloguj, QtCore.SIGNAL("clicked()"), self.doLogin)

    def doLogin(self):          
        with dbconnect():
            cur = dbconnect().cursor()

我得到的错误是:

Traceback (most recent call last):
  File "main.py", line 59, in doLogin
    with dbconnect():
AttributeError: __exit__

:编辑2:

在unutbu的回答之后,以及我对代码的一些摆弄,这是我正在寻找的解决方案:

con = None

def dbconnect():
    global con
    try:
        if os.name == 'nt': 
            con = lite.connect(host='127.0.0.1', user='ivica',passwd='pass',db='baza',charset='utf8')
        else:
            con = lite.connect(host='127.0.0.1',unix_socket='/run/mysqld/mysqld.sock', user='ivica',passwd='pass',db='baza',charset='utf8')
    except lite.err.OperationalError as err:
        msgBox = QtGui.QMessageBox()
        msgBox.setText(str(err))
        msgBox.show()
    return con

class Logon(QtGui.QDialog):
    def __init__(self):
        QtGui.QDialog.__init__(self)
        self.ui=Ui_dlgLogovanje()
        self.ui.setupUi(self)
        QtCore.QObject.connect(self.ui.dugmeUloguj, QtCore.SIGNAL("clicked()"), self.doLogin)

    def doLogin(self):      
        if con == None:
            reply = QtGui.QMessageBox.warning(self, 'Greška',
            "Can't establish connection to database!", QtGui.QMessageBox.Ok)
            if reply == QtGui.QMessageBox.Ok:
                self.close() #and when user clicks OK program closes

        else:
        with dbconnect():
            cur = dbconnect().cursor()
                    #do other database stuff, check credentials etc.

1 个答案:

答案 0 :(得分:1)

使用try...except块来处理OperationalError例外:

import sys
from PyQt4 import QtGui
import pymysql as lite


def dbconnect():
    global con
    config = {
        'host' : '127.0.0.1',
        'user' = 'ivica',
        'passwd' = 'pass',
        'db' = 'baza',
        'charset' = 'utf8'
        }
    try:
        if os.name == 'nt':
            con = lite.connect(**config)
        else:
            con = lite.connect(unix_socket = '/run/mysqld/mysqld.sock', **config))
    except lite.err.OperationalError as err:
        msgBox = QtGui.QMessageBox()
        msgBox.setText(str(err))
        msgBox.exec_()

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    con = None
    dbconnect()
    if con is not None:
        sys.exit(app.exec_())

听起来MySQL连接是程序的核心部分,因此如果连接过程不成功,您最好在开始时建立连接或退出。

另外,使用

with dbconnect():
    ...

与定义全局con不兼容,因为当Python退出with - 块时连接已关闭。