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PODisplay MySQL error in QMessageBox
 

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  1. PODisplay MySQL error in QMessageBox
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    <p>I'm running a local MySQL server for developing my PyQt application. It would be nice if I could display a QMessageBox if server is down, so that endusers would have some idea why is application not starting.</p> <p>If I shut down the server and run my program from terminal, I get the usual response:</p> <p><code>pymysql.err.OperationalError: (2003, "Can't connect to MySQL server on '127.0.0.1' (2)")</code></p> <p>my code is simple</p> <pre><code>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... </code></pre> <p>Is there a way for me to actually display a QMessageBox stating "MySQL server is down!" or something similar? If MySQL server is not running, my application window will not even show, just the terminal error.</p> <p>:EDIT:</p> <p>After proposed changes, my code looks like this:</p> <pre><code>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() </code></pre> <p>and error I get is:</p> <pre><code>Traceback (most recent call last): File "main.py", line 59, in doLogin with dbconnect(): AttributeError: __exit__ </code></pre> <p>:EDIT 2:</p> <p>After unutbu's answer, and some of my fiddling with the code, this is the solution I was looking for:</p> <pre><code>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. </code></pre>
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    1. USivica
    1. USivica
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    1. CODo you get this `AttributeError` only when `lite.connect` fails, or do you get it even if a successful connection is made?
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      1. USunutbu
    2. COIf there is no MySQL server running, that is the error I get. If the server is running everything is fine, no errors.
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      1. USivica
    3. COWhen the connection fails, `con` equals `None`, which does not have an `__exit__` method. This is why the `with dbconnect()` fails. What do you want to happen if the connection fails?
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      1. USunutbu
 

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