简介

通过定时器Timer触发事件，定时更新绘图，可以形成动态更新图片。下面的实例是学习《matplotlib for python developers》一文的笔记。

实现

实现代码及简单介绍

通过self.user = self.user[1:] + [temp]，每次删除列表的第一元素，在其尾部添加新的元素。这样完成user数据的动态更新。其他详细的解释见文中的注释部分。

#-*-coding:utf-8-*- import wx from matplotlib.figure import Figure import matplotlib.font_manager as font_manager import numpy as np from matplotlib.backends.backend_wxagg import \ FigureCanvasWxAgg as FigureCanvas # wxWidgets object ID for the timer TIMER_ID = wx.NewId() # number of data points POINTS = 300 class PlotFigure(wx.Frame): """Matplotlib wxFrame with animation effect""" def __init__(self): wx.Frame.__init__(self, None, wx.ID_ANY, title="CPU Usage Monitor", size=(600, 400)) # Matplotlib Figure self.fig = Figure((6, 4), 100) # bind the Figure to the backend specific canvas self.canvas = FigureCanvas(self, wx.ID_ANY, self.fig) # add a subplot self.ax = self.fig.add_subplot(111) # limit the X and Y axes dimensions self.ax.set_ylim([0, 100]) self.ax.set_xlim([0, POINTS]) self.ax.set_autoscale_on(False) self.ax.set_xticks([]) # we want a tick every 10 point on Y (101 is to have 10 self.ax.set_yticks(range(0, 101, 10)) # disable autoscale, since we don't want the Axes to ad # draw a grid (it will be only for Y) self.ax.grid(True) # generates first "empty" plots self.user = [None] * POINTS self.l_user,=self.ax.plot(range(POINTS),self.user,label='User %') # add the legend self.ax.legend(loc='upper center', ncol=4, prop=font_manager.FontProperties(size=10)) # force a draw on the canvas() # trick to show the grid and the legend self.canvas.draw() # save the clean background - everything but the line # is drawn and saved in the pixel buffer background self.bg = self.canvas.copy_from_bbox(self.ax.bbox) # bind events coming from timer with id = TIMER_ID # to the onTimer callback function wx.EVT_TIMER(self, TIMER_ID, self.onTimer) def onTimer(self, evt): """callback function for timer events""" # restore the clean background, saved at the beginning self.canvas.restore_region(self.bg) # update the data temp =np.random.randint(10,80) self.user = self.user[1:] + [temp] # update the plot self.l_user.set_ydata(self.user) # just draw the "animated" objects self.ax.draw_artist(self.l_user)# It is used to efficiently update Axes data (axis ticks, labels, etc are not updated) self.canvas.blit(self.ax.bbox) if __name__ == '__main__': app = wx.PySimpleApp() frame = PlotFigure() t = wx.Timer(frame, TIMER_ID) t.Start(50) frame.Show() app.MainLoop()

运行结果如下所示：

疑问

但程序运行在关闭的时候会出现应用程序错误，不知道什么问题。python不是有垃圾回收机制吗，难道是内存泄露？

猜测的原因可能是在关闭的时候正在绘图故导致应用程序出错。通过添加Frame的析构函数,停止更新则不会出现问题。

def __del__( self ): t.Stop()

总结

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