LabRAD Tips

GUI Tips

qt4reactor:

• Whenever using twisted (i.e. LabRAD) with PyQt4, qt4reactor.py must be instantiated before twisted. Even 'import LabRAD' must come after qt4reactor. Doing otherwise will result in a "reactor already installed" error.

  if __name__ == "__main__":
      a = QtGui.QApplication( [] )
      import qt4reactor
      qt4reactor.install()
      from twisted.internet import reactor
      histogrammer = Histogrammer(reactor)
      histogrammer.show()
      reactor.run()

• If integrating PyQt4 with a LabRAD server, make sure to instantiate qt4reactor before importing the server:

  from PyQt4 import QtGui
  a = QtGui.QApplication( [] )
  import qt4reactor
  qt4reactor.install()  
  from labrad.server import LabradServer, setting, Signal

• Special note: if your LabRAD server inherits from a parent LabRAD server, make sure you import QtGui in the parent server as well!

  from PyQt4 import QtGui

• Misc: When creating a new window, if the window opens and immediately closes, this is because the window might be assigned to a temporary variable which is deleted as soon as the function finishes. Ex:

  def createWindow(self)
      newWindow = NewWindow(self)

This window will close. If the new window is instantiated as an object of the parent class, then the window will persist.

def createWindow(self)
    self.newWindow = NewWindow(self)