content: # Python Qt4 bindings for GUI objects
  from PyQt4 import QtGui
  # import the Qt4Agg FigureCanvas object, that binds Figure to
  # Qt4Agg backend. It also inherits from QWidget
  from matplotlib.backends.backend_qt4agg \
  import FigureCanvasQTAgg as FigureCanvas
  # Matplotlib Figure object
  from matplotlib.figure import Figure
  
  
  class MplCanvas(FigureCanvas):
      """Class to represent the FigureCanvas widget"""
      def __init__(self):
          # setup Matplotlib Figure and Axis
          self.fig = Figure()
          self.ax = self.fig.add_subplot(111)
          # initialization of the canvas
          FigureCanvas.__init__(self, self.fig)
          # we define the widget as expandable
          FigureCanvas.setSizePolicy(self,
          QtGui.QSizePolicy.Expanding,
          QtGui.QSizePolicy.Expanding)
          # notify the system of updated policy
          FigureCanvas.updateGeometry(self)
  
  
  class MplWidget(QtGui.QWidget):
      """Widget defined in Qt Designer"""
      def __init__(self, parent = None):
          # initialization of Qt MainWindow widget
          QtGui.QWidget.__init__(self, parent)
          # set the canvas to the Matplotlib widget
          self.canvas = MplCanvas()
          # create a vertical box layout
          self.vbl = QtGui.QVBoxLayout()
          # add mpl widget to vertical box
          self.vbl.addWidget(self.canvas)
          # set the layout to th vertical box
          self.setLayout(self.vbl)