How to use thread with matplotlib on wxpython

Question

I want to use another thread for matplotlib. But when I run below script, it gives an error timer can only be started from the main thread . Any help would be appreciated.

import wx
from threading import Thread
import serial
import threading
import time
import matplotlib.pyplot as plt
import matplotlib.animation as animation

fig, ax1 = plt.subplots( )  
def runA():
    print("THREAD")
    while True:
        def mix(i)
            x=[1,3,5]
            y=[13,5,23]
            plt.plot(x,y)
            time.sleep(1)
        ani =animation. FuncAnimation(fig,mix)
        plt.show()

class MyFrame1 ( wx.Frame ):
    def __init__ (self, parent):
        wx.Frame.__init__(self, parent)
        self.SetSizeHints( wx.Defaultsize, wx.DefaultSize)
        bSizer3= wx.BoxSizer(wx.VERTICAL)

        self.button1= wx.Button( self, wx.ID_ANY, "mybutton1", wx.DefaultPosition, wx.DefaultSize, 0)

        bsizer3.Add( self.button1, 1, wx.ALL|wx.EXPAND, 5)

        self.button2= wx.Button( self, wx.ID_ANY, "mybutton2", wx.DefaultPosition, wx.DefaultSize, 0)

        bsizer3.Add( self.button2, 1, wx.ALL|wx.EXPAND, 5)
        self SetSizer( bsizer3)
        self.Layout ()
        self.Centre( wx. BOTH )
# Connect Events
        self.button1.Bind(wx.EVT_BUTTON, self.b1_f )
        self.button2.Bind(wx.EVT_BUTTON, self.b2_f )

    def b1_f( self, event ):
        t2=Thread (target =runA)
        t2.start()

    def b2_f( self, event):
        print("heLLo")

if __name__ == "__main__":
    app = wx.App(False)
    frame=MyFrame1 (None)
    frame.Show(True)
    app.MainLoop()

Note: Actually wxpython has its own plot library. But I couldn't succeed image read and plot data on it.

Answer 1

There were several issues with the code in your question. The following line does not work in wxPython 4.0.4, self.SetSizeHints( wx.Defaultsize, wx.DefaultSize) and you used different names for the wx.BoxSizer . Regarding the question, I could not reproduce your error but I think the problem is that you need to move the plotting code to class MyFrame1 . One way to do it is:

import wx
from threading import Thread
import serial
import threading
import time
import matplotlib.pyplot as plt
import matplotlib.animation as animation

class MyFrame1(wx.Frame):
    def __init__ (self, parent):
        wx.Frame.__init__(self, parent)
        #self.SetSizeHints(wx.Defaultsize, wx.DefaultSize)
        bSizer3= wx.BoxSizer(wx.VERTICAL)

        self.button1 = wx.Button(self, wx.ID_ANY, "mybutton1", 
                                 wx.DefaultPosition, wx.DefaultSize, 0)

        bSizer3.Add(self.button1, 1, wx.ALL|wx.EXPAND, 5)

        self.button2 = wx.Button(self, wx.ID_ANY, "mybutton2", 
                                 wx.DefaultPosition, wx.DefaultSize, 0)

        bSizer3.Add(self.button2, 1, wx.ALL|wx.EXPAND, 5)
        self.SetSizer(bSizer3)
        self.Layout()
        self.Centre(wx.BOTH)
# Connect Events
        self.button1.Bind(wx.EVT_BUTTON, self.b1_f)
        self.button2.Bind(wx.EVT_BUTTON, self.b2_f)

    def b1_f( self, event ):
        print('Hello2')
        t2=Thread(target = self.runA)
        t2.start()

    def b2_f( self, event):
        print("heLLo")


    def runA(self):
        fig, ax1 = plt.subplots( )  
        print("THREAD")
        while True:
            def mix(i):
                x=[1,3,5]
                y=[13,5,23]
                plt.plot(x,y)
                time.sleep(1)
            ani = animation.FuncAnimation(fig,mix)
            plt.show()

if __name__ == "__main__":
    app = wx.App()
    frame=MyFrame1(None)
    frame.Show()
    app.MainLoop()

Now this work but:

1 - You should consider using the wxAgg backend for matplotlib . The backend you are using now gives a non-fatal error when you make a plot, close it and plot again. Also, it works in Win10 and Linux(Fedora 30) but it does not work on macOS 10.14.4. Here is an example .

2 - You need to find a way to deactivate/activate button1 because with the current matplotlib backend you cannot have two plot at the same time. So clicking the button while the plot is shown makes the GUI unresponsive.

3 - The timer in the plotting function makes the plot unresponsive. Perhaps matplotlib has another way to control the speed of the animation.