python之matplotlib学习绘制动态更新图实例代码

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

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() 

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