title: How could i pass parameter to pika callback
body: <p>I use pika to interact with RabbitMQ server as following:
  1. P1 send message to RabbitMQ
  2. C1 is an pyqt4 desktop tray application,which will show the above message once received.
  The code is as following:</p>
  
  <pre><code>import sip
  sip.setapi('QVariant', 2)
  
  from PyQt4 import QtCore, QtGui
  
  import systray_rc
  
  
  class Window(QtGui.QDialog):
      def __init__(self):
          super(Window, self).__init__()
  
          self.createIconGroupBox()
          self.createMessageGroupBox()
  
          self.iconLabel.setMinimumWidth(self.durationLabel.sizeHint().width())
  
          self.createActions()
          self.createTrayIcon()
  
          self.showMessageButton.clicked.connect(self.showMessage)
          self.showIconCheckBox.toggled.connect(self.trayIcon.setVisible)
          self.iconComboBox.currentIndexChanged.connect(self.setIcon)
          self.trayIcon.messageClicked.connect(self.messageClicked)
          self.trayIcon.activated.connect(self.iconActivated)
  
          mainLayout = QtGui.QVBoxLayout()
          mainLayout.addWidget(self.iconGroupBox)
          mainLayout.addWidget(self.messageGroupBox)
          self.setLayout(mainLayout)
  
          self.iconComboBox.setCurrentIndex(1)
          self.trayIcon.show()
  
          self.setWindowTitle("Systray")
          self.resize(400, 300)       
  
  
  
      def setVisible(self, visible):
          self.minimizeAction.setEnabled(visible)
          self.maximizeAction.setEnabled(not self.isMaximized())
          self.restoreAction.setEnabled(self.isMaximized() or not visible)
          super(Window, self).setVisible(visible)
  
      def closeEvent(self, event):
          if self.trayIcon.isVisible():
              QtGui.QMessageBox.information(self, "Systray",
                      "The program will keep running in the system tray. To "
                      "terminate the program, choose &lt;b&gt;Quit&lt;/b&gt; in the "
                      "context menu of the system tray entry.")
              self.hide()
              event.ignore()
  
      def setIcon(self, index):
          icon = self.iconComboBox.itemIcon(index)
          self.trayIcon.setIcon(icon)
          self.setWindowIcon(icon)
  
          self.trayIcon.setToolTip(self.iconComboBox.itemText(index))
  
      def iconActivated(self, reason):
          if reason in (QtGui.QSystemTrayIcon.Trigger, QtGui.QSystemTrayIcon.DoubleClick):
              self.iconComboBox.setCurrentIndex(
                      (self.iconComboBox.currentIndex() + 1)
                      % self.iconComboBox.count())
          elif reason == QtGui.QSystemTrayIcon.MiddleClick:
              self.showMessage()
  
      def showMessage(self):
          icon = QtGui.QSystemTrayIcon.MessageIcon(
                  self.typeComboBox.itemData(self.typeComboBox.currentIndex()))
  #        self.trayIcon.showMessage(self.titleEdit.text(),
  #                self.bodyEdit.toPlainText(), icon,
  #                self.durationSpinBox.value() * 1000)
          self.trayIcon.showMessage('stock alarm',
                  'test', icon,
                  self.durationSpinBox.value() * 1000)
  
      def messageClicked(self):
          QtGui.QMessageBox.information(None, "Systray",
                  "Sorry, I already gave what help I could.\nMaybe you should "
                  "try asking a human?")
  
      def createIconGroupBox(self):
          self.iconGroupBox = QtGui.QGroupBox("Tray Icon")
  
          self.iconLabel = QtGui.QLabel("Icon:")
  
          self.iconComboBox = QtGui.QComboBox()
          self.iconComboBox.addItem(QtGui.QIcon(':/images/bad.svg'), "Bad")
          self.iconComboBox.addItem(QtGui.QIcon(':/images/heart.svg'), "Heart")
          self.iconComboBox.addItem(QtGui.QIcon(':/images/trash.svg'), "Trash")
  
          self.showIconCheckBox = QtGui.QCheckBox("Show icon")
          self.showIconCheckBox.setChecked(True)
  
          iconLayout = QtGui.QHBoxLayout()
          iconLayout.addWidget(self.iconLabel)
          iconLayout.addWidget(self.iconComboBox)
          iconLayout.addStretch()
          iconLayout.addWidget(self.showIconCheckBox)
          self.iconGroupBox.setLayout(iconLayout)
  
      def createMessageGroupBox(self):
          self.messageGroupBox = QtGui.QGroupBox("Balloon Message")
  
          typeLabel = QtGui.QLabel("Type:")
  
          self.typeComboBox = QtGui.QComboBox()
          self.typeComboBox.addItem("None", QtGui.QSystemTrayIcon.NoIcon)
          self.typeComboBox.addItem(self.style().standardIcon(
                  QtGui.QStyle.SP_MessageBoxInformation), "Information",
                  QtGui.QSystemTrayIcon.Information)
          self.typeComboBox.addItem(self.style().standardIcon(
                  QtGui.QStyle.SP_MessageBoxWarning), "Warning",
                  QtGui.QSystemTrayIcon.Warning)
          self.typeComboBox.addItem(self.style().standardIcon(
                  QtGui.QStyle.SP_MessageBoxCritical), "Critical",
                  QtGui.QSystemTrayIcon.Critical)
          self.typeComboBox.setCurrentIndex(1)
  
          self.durationLabel = QtGui.QLabel("Duration:")
  
          self.durationSpinBox = QtGui.QSpinBox()
          self.durationSpinBox.setRange(5, 60)
          self.durationSpinBox.setSuffix(" s")
          self.durationSpinBox.setValue(15)
  
          durationWarningLabel = QtGui.QLabel("(some systems might ignore this "
                  "hint)")
          durationWarningLabel.setIndent(10)
  
          titleLabel = QtGui.QLabel("Title:")
  
          self.titleEdit = QtGui.QLineEdit("Cannot connect to network")
  
          bodyLabel = QtGui.QLabel("Body:")
  
          self.bodyEdit = QtGui.QTextEdit()
          self.bodyEdit.setPlainText("Don't believe me. Honestly, I don't have "
                  "a clue.\nClick this balloon for details.")
  
          self.showMessageButton = QtGui.QPushButton("Show Message")
          self.showMessageButton.setDefault(True)
  
          messageLayout = QtGui.QGridLayout()
          messageLayout.addWidget(typeLabel, 0, 0)
          messageLayout.addWidget(self.typeComboBox, 0, 1, 1, 2)
          messageLayout.addWidget(self.durationLabel, 1, 0)
          messageLayout.addWidget(self.durationSpinBox, 1, 1)
          messageLayout.addWidget(durationWarningLabel, 1, 2, 1, 3)
          messageLayout.addWidget(titleLabel, 2, 0)
          messageLayout.addWidget(self.titleEdit, 2, 1, 1, 4)
          messageLayout.addWidget(bodyLabel, 3, 0)
          messageLayout.addWidget(self.bodyEdit, 3, 1, 2, 4)
          messageLayout.addWidget(self.showMessageButton, 5, 4)
          messageLayout.setColumnStretch(3, 1)
          messageLayout.setRowStretch(4, 1)
          self.messageGroupBox.setLayout(messageLayout)
  
      def createActions(self):
          self.minimizeAction = QtGui.QAction("Mi&amp;nimize", self,
                  triggered=self.hide)
  
          self.maximizeAction = QtGui.QAction("Ma&amp;ximize", self,
                  triggered=self.showMaximized)
  
          self.restoreAction = QtGui.QAction("&amp;Restore", self,
                  triggered=self.showNormal)
  
          self.quitAction = QtGui.QAction("&amp;Quit", self,
                  triggered=QtGui.qApp.quit)
  
      def createTrayIcon(self):
           self.trayIconMenu = QtGui.QMenu(self)
           self.trayIconMenu.addAction(self.minimizeAction)
           self.trayIconMenu.addAction(self.maximizeAction)
           self.trayIconMenu.addAction(self.restoreAction)
           self.trayIconMenu.addSeparator()
           self.trayIconMenu.addAction(self.quitAction)
  
           self.trayIcon = QtGui.QSystemTrayIcon(self)
           self.trayIcon.setContextMenu(self.trayIconMenu)
  
  def callback(ch, method, properties, body):
          print " [x] %r:%r" % (method.routing_key, body,)
          #window.showMessage = body
          #window.showMessage()
          #self.showMessage()
  
  def subsribeRabbit():
      import pika
      import sys
      from util import settings
  
      connection = pika.BlockingConnection(pika.ConnectionParameters(
              host=settings.RABBIT_SERVER))
      channel = connection.channel()
  
      channel.exchange_declare(exchange=settings.STOCK_ALARMS_TOPIC,
                               type='topic')
  
      result = channel.queue_declare(exclusive=True)
      queue_name = result.method.queue
  
      binding_keys = '#'
  
      for binding_key in binding_keys:
          channel.queue_bind(exchange=settings.STOCK_ALARMS_TOPIC,
                             queue=queue_name,
                             routing_key=binding_key)
  
      print ' [*] Waiting for logs. To exit press CTRL+C'
  
  
      channel.basic_consume(callback,
                            queue=queue_name,
                            no_ack=True)
  
      channel.start_consuming()
  
  if __name__ == '__main__':
  
      import sys
      from cron.realtimemonitorschedule import startMonitor    
  
      app = QtGui.QApplication(sys.argv)
  
      if not QtGui.QSystemTrayIcon.isSystemTrayAvailable():
          QtGui.QMessageBox.critical(None, "Systray",
                  "I couldn't detect any system tray on this system.")
          sys.exit(1)
  
      QtGui.QApplication.setQuitOnLastWindowClosed(False)
  
      window = Window()
      window.show()   
      from threading import Thread
      thread = Thread(target = subsribeRabbit)
      thread.start()
      #thread.join()
  
      sys.exit(app.exec_())  
  </code></pre>
  
  <p>The question is that how could i call window.showMessage in the callback() function?Thanks in advance, i'm new to both Python and RabbitMQ.</p>