使用 Matplotlib 和 PyQt 进行动态绘图 - 冻结窗口

Question

目标：

我想在 pyQt4 GUI 窗口中嵌入 Matplotlib 图。剧情要及时更新。

问题：

窗口冻结，直到绘图完成。我希望情节实时更新。

上下文：

我们有数值算法正在处理一些数据，我希望该图显示数据集如何受到算法的影响。该算法每 0.5 秒完成一次迭代 - 每次迭代都必须更新绘图。

测试代码：

算法替换为test()，它绘制一个随机点 100 次。下面的代码说明了问题：

import sys
from PlotGUI import *
import threading
from random import randint
import time

class GUIForm(QtGui.QDialog):

    def __init__(self, parent=None):
        QtGui.QWidget.__init__(self,parent)
        self.ui = Ui_Dialog()
        self.ui.setupUi(self)
        QtCore.QObject.connect(self.ui.pushButton, QtCore.SIGNAL('clicked()'), self.startSim)
        self.cPlot = None # custom plotter
        self.instantiatePlot()        

    def instantiatePlot(self):
        self.cPlot = CustomPlotter(self.ui.widget.canvas) 
        self.cPlot.prepareFigure()

    def startSim(self):
        self.cPlot.clear();        
        draw_thread = threading.Thread(target=self.cPlot.test())
        draw_thread.start()

class CustomPlotter():
    def __init__(self, canvas):
        print 'constructor'
        self.canvas = canvas        

    def prepareFigure(self):
        ax = self.canvas.ax

        ax.set_ylim([-1,101])
        #ax.set_xlim([dt[0],dt[1]])
        ax.set_ylim([-1, 10])
        self.canvas.draw()

    def clear(self):
        self.canvas.ax.clear()

    def test(self):
        canvas = self.canvas 
        ax = canvas.ax
        for x in range(0,100):
            y = randint(0,9)
            ax.plot(x, y, 'ro')
            print x
            canvas.draw()
            time.sleep(1)
            #canvas.show()
            #canvas.update()

if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)
    myapp = GUIForm()
    myapp.show()
    sys.exit(app.exec_())

提前致谢。这是一些原型设计，所以我愿意接受所有提供快速解决方案的选项/替代方案。

Answer 1

尝试实例化新线程时出现错误：

draw_thread = threading.Thread(target=self.cPlot.test())

这将立即在当前线程中执行测试方法，然后将结果（None）作为target 传递。您可能想要做的是：

draw_thread = threading.Thread(target=self.cPlot.test)

Thread(target=None) 只是创建一个什么都不做的线程，只是立即退出，因此是有效的，不会产生任何表明此问题的异常。

因为test() 方法是在GUI 线程中启动的，所以GUI 会被阻塞，直到方法返回。

Answer 2

PySide/Qt 无法从另一个线程更新小部件（QPixmap/显示项）。您不能直接在另一个线程中为 GUI 项目调用 plot。

参见 matplotlib.animation.FuncAnimation。 http://matplotlib.org/api/animation_api.html

import numpy as np

# ========== Matplotlib [PySide] ==========
import matplotlib
matplotlib.use("Qt4Agg")
matplotlib.rcParams["backend.qt4"] = "PySide"

import matplotlib.animation as mplanimation
from matplotlib.figure import Figure
from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas

class InteractivePlotWidget(FigureCanvas):

    def __init__(self):
        super().__init__(Figure(tight_layout=True))
        self.axes = self.figure.add_subplot(111)

        self.setSizePolicy(QtGui.QSizePolicy.Expanding, QtGui.QSizePolicy.Expanding)

        self.name = ""
        self.data = np.zeros(shape=(100, 2))
    # end __init__

    def plot_data(self, interval=0):
        data = np.array([(i, np.sin(i)) for i in range(interval)])
        try:
            self.axes.lines[0].set_data(data[:,0], data[:,1])
        except IndexError:
            self.axes.plot(data, label=self.name) # Lots of overhead. Do once.

        self.axes.relim()
        self.axes.autoscale_view(True, True, True)
        return self.axes.lines  # animation handles draw
        # manually trigger draw
        # self.draw_idle()
        # self.flush_events()
    # end plot_data
# end class InteractivePlotWidget

if __name__ == "__main__":
    QtGui.QApplication([])

    w = InteractivePlotWidget()
    w.show()

    # Create and start the animation (timer)
    anim = mplanimation.FuncAnimation(w.figure, w.plot_data, interval=0)
    anim._start()

    sys.exit(QtGui.qApp.exec_())

Answer 3

matplotlib 库中的 embedding_in_qt4.py 示例应该足够了，对吧？

# ...
class MyMplCanvas(FigureCanvas):
    """Ultimately, this is a QWidget (as well as a FigureCanvasAgg, etc.)."""

    def __init__(self, parent=None, width=5, height=4, dpi=100):
        fig = Figure(figsize=(width, height), dpi=dpi)
        self.axes = fig.add_subplot(111)
        # We want the axes cleared every time plot() is called
        self.axes.hold(False)

        self.compute_initial_figure()

        #
        FigureCanvas.__init__(self, fig)
        self.setParent(parent)

        FigureCanvas.setSizePolicy(self,
                                   QtGui.QSizePolicy.Expanding,
                                   QtGui.QSizePolicy.Expanding)
        FigureCanvas.updateGeometry(self)

    def compute_initial_figure(self):
        pass
# ...
class MyDynamicMplCanvas(MyMplCanvas):
    """A canvas that updates itself every second with a new plot."""

    def __init__(self, *args, **kwargs):
        MyMplCanvas.__init__(self, *args, **kwargs)
        timer = QtCore.QTimer(self)
        timer.timeout.connect(self.update_figure)
        timer.start(1000)

    def compute_initial_figure(self):
        self.axes.plot([0, 1, 2, 3], [1, 2, 0, 4], 'r')

    def update_figure(self):
        # Build a list of 4 random integers between 0 and 10 (both inclusive)
        l = [random.randint(0, 10) for i in range(4)]

        self.axes.plot([0, 1, 2, 3], l, 'r')
        self.draw()
# ...