Re: Plotting to a matplotlib / pyplot window does not work

#!/usr/bin/env python3


# Example showing how I cannot make pyplot work to plot data in a pyplot window
# (1) Show GUI with a button to start running a measurement instrument
# (2) Once the button is pressed, run the measurement instrument:
#	- Get a new data value every second
# 	- After getting a new value, plot all data in a pyplot window <-- *** THIS DOES NOT SEEM TO WORK ***
#
# The problem is that the pyplot window does not seem to show up on the screen.

import time
import random
from threading import Thread
import wx
from matplotlib import pyplot as plt


# measurement instrument that takes measurement data and plots data in a pyplot window
class instrument:

	def __init__(self):
	
		# init the instrument
		self.values = [] # container list of the measurement values
		
		# set up plotting:
		self.fig  = plt.figure(figsize=(200,100))      # pyplot figure
		self.axes = self.fig.add_subplot(1,1,1)        # pyplot axes
		plt.ion()                                      # non-blocking pyplot operation ("interactive mode")
		self.fig.show()                                # show the pyplot window <-- *** THIS DOES NOT SEEM TO WORK ***
	
	def read_value(self):
		# get a (fake) measurement value
		print('Getting a new data value...')
		val = random.random()                          # determine a (fake) data value
		self.values.append(val)                        # append the value to list of previous values
		return val
	
	def plot_data(self):
		print('Plotting the data...')
		self.axes.cla()                                # clear plot data
		self.axes.plot(self.values)                    # plot all data
		

# Thread that gets measurement data from the instrument, with logging to pyplot window
class measurement_thread(Thread):

	def __init__(self, main_window):
		Thread.__init__(self)
		self.main_window = main_window

	def run(self):
		# get data from instrument and plot the data in pyplot window
		while True:
			self.main_window.instrument.read_value()               # get a measurement value
			wx.CallAfter( self.main_window.instrument.plot_data )  # update the pyplot figure <-- *** THIS NEEDS TO BE IN wx.CallAfter TO AVOID CRASHING, BUT I DON'T UNDERSTAND WHY ***
			time.sleep(1)                                          # wait a bit for the next measurement


# main window:
class MyFrame(wx.Frame):
  
	def __init__(self):
	
		# define GUI:
		wx.Frame.__init__(self, None, title="Instrument Control", size=(200,100))
		panel = wx.Panel(self)
		button = wx.Button(panel, label='Start measurements')
		button.Bind(wx.EVT_BUTTON, self.on_button_press)
		sizer = wx.BoxSizer(wx.VERTICAL)
		sizer.Add(button, 1, wx.ALL | wx.CENTER, 25)
		panel.SetSizer(sizer)    
		
		# measurement instrument, and thread for measurements:
		self.instrument = instrument()
		self.measurement_thread = measurement_thread(self)
		
		# show the window:
		self.Show()

	def on_button_press(self, event):
        	print('Starting the measurement thread...')
        	self.measurement_thread.start() # start the measurement thread


# main:
if __name__ == '__main__':
	app = wx.App()
	frame = MyFrame()
	app.MainLoop()