from matplotlib import pyplot as plt
from PyQt4.QtGui import QWidget, QVBoxLayout
from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg


class Test(QWidget):
    def __init__(self, parent=None):
        QWidget.__init__(self, parent)
        self.canvas = FigureCanvasQTAgg(self.test_fig())
        self.layout = QVBoxLayout(self)
        self.layout.addWidget(self.canvas)

        while True:
            self.update_fig()

    def update_fig(self):
        self.canvas.figure = self.test_fig() 
        self.canvas.draw()
    
    def test_fig(self):
        fig = plt.figure()
        ax1 = fig.add_subplot(111)
        line, = ax1.plot([1,2,3], [4,5,6])
        return fig

if __name__ == "__main__":
    import sys
    from PyQt4.QtGui import QApplication
    app = QApplication(sys.argv)
    main = Test()
    main.show()
    app.exec_()