[Matplotlib-users] a memory leak in matplotlib plot embedded in wxpython

[Barraclough, D. \(e. 414\) <dj...@qv...>]

 

I'm using matplotlib plots embedded in a wxpython application to display
a stream of data. The application works effectively but I have noticed
that memory usage rises substantially over time (if left long enough the
process can go from 50MB to near 1GB of RAM). After some
experimentation, I have tracked the problem down to the canvas.draw()
call needed to refresh my matplotlib plos. Thinking that the problem may
be due to how I coded up my plots I looked to see if the problem was
present in the examples given at

 

http://matplotlib.sourceforge.net/examples/user_interfaces

 

and found that the problem seem to be present in some the examples
posted there if I added a timer to cause the canvas draw to be
repeatedly performed. 

 

 

The example below is based on  

 

http://matplotlib.sourceforge.net/examples/user_interfaces/embedding_in_
wx2.html

 

and has been instrumented to report memory usage when running in
Windows. My tests indicate that working set memory rises by 11 to 12
Kbytes at each plot. 

 

Some what to my surprise, I found the same issue when I ran an even
simpler version on a linux mint virtual box running on my win7 system.
(I have not explored this much so somebody else might want to test
things on a non virtual linux box)  I assume this implies that python is
probably keeping something alive that was expected to be automatically
cleaned up at each draw. I have made some effort to localize the problem
further but right now I don't have the necessary  time to get heavily
into the inner workings of matplotlib or wxpython 

 

Has any body else seen this problem before, and if so, has any body a
work around that allows rapid replotting - I would guess that I could
periodically flush the figure and re build my plots but this would cause
periodic glitches in plotting? 

 

 

Dominic

 

 

System details

 

Win7 ultimate service pack1

Python 2.6.6 (but I've seen the problem with python2.5 and 2.7)

Matplotlib 1.1.1 (but also in earlier versions)

Wxpython 2.9.4.0 msw (classic) (put also on 2.8.12.0 unicode)

 

 

Example 

------------------------------------------------------------------------
-----------------------------------------------------------

import wxversion

wxversion.ensureMinimal('2.8')

 

from numpy import arange, sin, pi

 

import matplotlib

 

# uncomment the following to use wx rather than wxagg

#matplotlib.use('WX')

#from matplotlib.backends.backend_wx import FigureCanvasWx as
FigureCanvas

 

# comment out the following to use wx rather than wxagg

matplotlib.use('WXAgg')

from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as
FigureCanvas

 

from matplotlib.backends.backend_wx import NavigationToolbar2Wx

 

from matplotlib.figure import Figure

import win32process

import wx

 

class CanvasFrame(wx.Frame):

 

    def __init__(self):

        wx.Frame.__init__(self,None,-1,

                         'CanvasFrame',size=(550,350))

 

        #self.SetBackgroundColour(wx.NamedColor("WHITE")) # 2.9 does not
like

 

        self.figure = Figure()

        self.axes = self.figure.add_subplot(111)

        t = arange(0.0,3.0,0.01)

        s = sin(2*pi*t)

 

        self.axes.plot(t,s)

        self.canvas = FigureCanvas(self, -1, self.figure)

 

        self.sizer = wx.BoxSizer(wx.VERTICAL)

        self.sizer.Add(self.canvas, 1, wx.LEFT | wx.TOP | wx.GROW)

        self.SetSizer(self.sizer)

        self.Fit()

 

        self.add_toolbar()  # comment this out for no toolbar

        self.timer = wx.Timer(self, -1)

        

        self.Bind(wx.EVT_TIMER, self.OnUpdate)

        self.delay = 200

        self.timer.Start(self.delay, oneShot = False)

        self.proc_id = win32process.GetCurrentProcess()

        adict = win32process.GetProcessMemoryInfo(self.proc_id)

        self.memory_old = adict["WorkingSetSize"]

        self.i = 0

        

    def add_toolbar(self):

        self.toolbar = NavigationToolbar2Wx(self.canvas)

        self.toolbar.Realize()

        if wx.Platform == '__WXMAC__':

            # Mac platform (OSX 10.3, MacPython) does not seem to cope
with

            # having a toolbar in a sizer. This work-around gets the
buttons

            # back, but at the expense of having the toolbar at the top

            self.SetToolBar(self.toolbar)

        else:

            # On Windows platform, default window size is incorrect, so
set

            # toolbar width to figure width.

            tw, th = self.toolbar.GetSizeTuple()

            fw, fh = self.canvas.GetSizeTuple()

            # By adding toolbar in sizer, we are able to put it at the
bottom

            # of the frame - so appearance is closer to GTK version.

            # As noted above, doesn't work for Mac.

            self.toolbar.SetSize(wx.Size(fw, th))

            self.sizer.Add(self.toolbar, 0, wx.LEFT | wx.EXPAND)

        # update the axes menu on the toolbar

        self.toolbar.update()

 

 

    def OnUpdate(self, evt):

        self.OnPaint( evt)

        self.i +=1

        the_count =25

        if self.i %the_count ==0:            

            adict_now = win32process.GetProcessMemoryInfo(self.proc_id)

            memory_now = adict_now["WorkingSetSize"]

            delta = (memory_now - self.memory_old )/ (the_count *1024.0)
#convert to kbytes per update

            self.memory_old = memory_now

            print "memory now = %i delta = %f\n" %(memory_now, delta)

        

    def OnPaint(self, event):

        self.canvas.draw()

 

class App(wx.App):

 

    def OnInit(self):

        'Create the main window and insert the custom frame'

        frame = CanvasFrame()

        frame.Show(True)

 

        return True

 

app = App(0)

app.MainLoop()