matplotlib - matplotlib not plot at the second time running in a thread

Question

I have a small program that plots a figure with 4 subplots. I make a little GUI and call that plotting function from a thread, so each time I click the button, it should recollect data and redraw that figure (with 4 subplot), without closing the script. The script can plot for the first time, however at the second time (click button without closing the script), it stops at initialize the subplots. I have tried plt.close('all'), plt.close(fig), plt.clf(),... but it doesnt help. I really run out of idea why it stops at the second time.

Here is my full little script. Much appreciate for any inputs

import sys, os
import time
import wx
import traceback
from textwrap import wrap
import shutil
import itertools
import numpy as np
import matplotlib
import matplotlib.pyplot as plt

import threading

def test():
    Do = Data()    
    Do.PlotGraph()

class Data(object):
    def __init__(self):       
        self.SavePath = "C:\\Plots\\"      

    def f(self, t):
        return np.exp(-t) * np.cos(2*np.pi*t)

    def PlotGraph(self):
        #Plotting
        print "***** Generating plot"
        t1 = np.arange(0.0, 5.0, 0.1)
        t2 = np.arange(0.0, 5.0, 0.02)

        print "Initialize subplots"
        fig, ((ax1, ax2), (ax3, ax4)) = plt.subplots(nrows = 2, ncols = 2, frameon=False, figsize=(20, 10))
        fontSize = 13

        print "Creating ax1"
        ax1title = "ax1" 
        ax1.set_title(ax1title, fontsize = fontSize)
        ax1.plot(t1, self.f(t1), 'bo', t2, self.f(t2), 'k')    

        print "Creating ax2"      
        ax2title = "ax2" 
        ax2.set_title(ax2title, fontsize = fontSize)
        ax2.plot(t1, self.f(t1), 'bo', t2, self.f(t2), 'k')

        print "Creating ax3"
        ax3title = "ax3" 
        ax3.set_title(ax3title, fontsize = fontSize)
        ax3.plot(t1, self.f(t1), 'bo', t2, self.f(t2), 'k')

        print "Creating ax4"
        ax4title = "ax4" 
        ax4.set_title(ax4title, fontsize = fontSize)
        ax4.plot(t1, self.f(t1), 'bo', t2, self.f(t2), 'k')

        fig.subplots_adjust(hspace = 0.35) #make room for axes title and x-axis label
        fig.subplots_adjust(bottom = 0.07) #make room for axes title and x-axis label
        fig.subplots_adjust(wspace = 0.30)
        fig.subplots_adjust(top = .86)

        filename= "Test"

        if not os.path.exists(self.SavePath):
            os.makedirs(self.SavePath)

        savefilename = self.unique_file(self.SavePath, filename, "png")        
        print "***** Saving plot to: " + self.SavePath + savefilename        
        fig.savefig(self.SavePath + savefilename, dpi = 200)
        plt.close(fig)

    def unique_file(self, path, basename, ext):
        actualname = "%s.%s" % (basename, ext)
        c = itertools.count()
        while os.path.exists(path + actualname):
            actualname = "%s_[%d].%s" % (basename, next(c), ext)
            #print "actualname: " + actualname
        return actualname 


################## THREAD UPDATE GUI ######################
#1. Create new custom event to update the display
DisplayEventType = wx.NewEventType();
EVT_DISPLAY = wx.PyEventBinder(DisplayEventType, 1);

def GetDataThreadStart(window):
    GetDataThread(window)

class GetDataThread(threading.Thread):    
    def __init__(self, output_window):
        threading.Thread.__init__(self)
        self.output_window = output_window
        print "Thread started"        
        self.start()

    def run(self):
        test()
        print "Test Done\n\n"
        self.UpdateFunction("Enable Go Button")     

    def UpdateFunction(self, msg):
        evt = UpdateDisplayEvent(DisplayEventType, -1) #initialize update display event
        evt.UpdateText(str(msg));  #update display event
        wx.PostEvent(self.output_window, evt)   

#Define event
class UpdateDisplayEvent(wx.PyCommandEvent):    
    def __init__(self, evtType, id):
        wx.PyCommandEvent.__init__(self, evtType, id)
        self.msg = ""  

    def UpdateText(self,text):
        self.msg = text

    def GetText(self):
        return self.msg


######## Define GUI ###########
class MyPanel(wx.Panel):
    def __init__(self, parent):
        wx.Panel.__init__(self, parent, -1)   

class MyFrame(wx.Frame):
    def __init__(self, parent):        
        self.title = 'Testing'
        wx.Frame.__init__(self, parent, -1, self.title, size = (300,350))                       

        pnl = MyPanel(self)                               

        self.Go_Button = wx.Button(pnl, -1, "Goooooo!")
        self.Bind(wx.EVT_BUTTON, self.ClickGo, self.Go_Button)       

        BoxSizerMain = wx.BoxSizer(wx.VERTICAL)      
        BoxSizerMain.Add(self.Go_Button, 0, wx.ALIGN_CENTER_HORIZONTAL)         
        self.Bind(EVT_DISPLAY, self.OnThreadUpdate)      

    def ClickGo(self, event):        
        self.Go_Button.Disable()
        GetDataThreadStart(self)           

    def OnThreadUpdate(self, event):
        msg = event.GetText()        
        if msg == "Enable Go Button":
            self.Go_Button.Enable()

def invokeGUI():
    app = wx.PySimpleApp()
    frame = MyFrame(None)
    frame.Show()
    frame.Iconize(True)
    frame.Iconize(False)
    frame.CenterOnScreen()
    app.MainLoop() 

if __name__ == '__main__':
    invokeGUI()

The result

Answer 1

I believe you need to change the matplotlib backend to wx via the matplotlib.use() function in order to embed matplotlib plots within wx graphics.

Here's what I changed in your script:

import matplotlib
matplotlib.use('WX')
import matplotlib.pyplot as plt

This produced the following image after testing:

Console output:

Initialize subplots
Creating ax1
Creating ax2
Creating ax3
Creating ax4
***** Saving plot to: /Users/luccary/Downloads/foo/Test_[0].png
/Users/luccary/.virtualenvs/numpy/lib/python2.7/site-packages/matplotlib/cbook.py:136: MatplotlibDeprecationWarning: The WX backend is deprecated. It's untested and will be removed in Matplotlib 2.2. Use the WXAgg backend instead. See Matplotlib usage FAQ for more info on backends.
  warnings.warn(message, mplDeprecation, stacklevel=1)
Test Done

Please note the deprecation warning, since wx will be removed as a backend in Matplotlib 2.2, and you should likely use wxagg instead.

References: See this matplotlib tutorial which I found after reading a Stack Overflow answer to a similar question here.

Hope that answers your question. Good luck!