QtSingleApplication for PySide or PyQt

Question

Is there a Python version of the C ++ QtSingleApplication from Qt Solutions ?

QtSingleApplication used to ensure that there can never be more than one instance of an application running at the same time.

Answer 1

Here is my own implementation. It has been tested with Python 2.7 and PySide 1.1.

It has essentially the same interface as the C ++ version of QtSingleApplication . The main difference is that you must provide a unique application identifier for the constructor. (By default, C ++ uses the path to the executable as a unique identifier that will not work here, since the executable will most likely be python.exe .)

 from PySide.QtCore import * from PySide.QtGui import * from PySide.QtNetwork import * class QtSingleApplication(QApplication): messageReceived = Signal(unicode) def __init__(self, id, *argv): super(QtSingleApplication, self).__init__(*argv) self._id = id self._activationWindow = None self._activateOnMessage = False # Is there another instance running? self._outSocket = QLocalSocket() self._outSocket.connectToServer(self._id) self._isRunning = self._outSocket.waitForConnected() if self._isRunning: # Yes, there is. self._outStream = QTextStream(self._outSocket) self._outStream.setCodec('UTF-8') else: # No, there isn't. self._outSocket = None self._outStream = None self._inSocket = None self._inStream = None self._server = QLocalServer() self._server.listen(self._id) self._server.newConnection.connect(self._onNewConnection) def isRunning(self): return self._isRunning def id(self): return self._id def activationWindow(self): return self._activationWindow def setActivationWindow(self, activationWindow, activateOnMessage = True): self._activationWindow = activationWindow self._activateOnMessage = activateOnMessage def activateWindow(self): if not self._activationWindow: return self._activationWindow.setWindowState( self._activationWindow.windowState() & ~Qt.WindowMinimized) self._activationWindow.raise_() self._activationWindow.activateWindow() def sendMessage(self, msg): if not self._outStream: return False self._outStream << msg << '\n' self._outStream.flush() return self._outSocket.waitForBytesWritten() def _onNewConnection(self): if self._inSocket: self._inSocket.readyRead.disconnect(self._onReadyRead) self._inSocket = self._server.nextPendingConnection() if not self._inSocket: return self._inStream = QTextStream(self._inSocket) self._inStream.setCodec('UTF-8') self._inSocket.readyRead.connect(self._onReadyRead) if self._activateOnMessage: self.activateWindow() def _onReadyRead(self): while True: msg = self._inStream.readLine() if not msg: break self.messageReceived.emit(msg) 

Here is a simple test program:

 import sys from PySide.QtGui import * from QtSingleApplication import QtSingleApplication appGuid = 'F3FF80BA-BA05-4277-8063-82A6DB9245A2' app = QtSingleApplication(appGuid, sys.argv) if app.isRunning(): sys.exit(0) w = QWidget() w.show() app.setActivationWindow(w) sys.exit(app.exec_()) 

Answer 2

You can see this blog post . This is for Pyside, but I think it will work with PyQt4 as well.