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
#       - The GUI locks up if the data rate is too high, and the data plotting is called too often (idle_time less than 0.1 in the measurement_thread)
#
# 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.backends.backend_wxagg import FigureCanvasWxAgg as FigureCanvas
from matplotlib.figure import Figure


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

	def __init__(self):
		self.values = []                               # container list of the measurement values
		self.plot_frame = instrument_plot_frame()      # frame for plotting measurement data recorded with the instrument
		self.plotting_in_progress = False
		
	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 (' + str(len(self.values)) + ' data points)...')
		self.plotting_in_progress = True
		self.plot_frame.Show(True)
		self.plot_frame.axes.cla()                     # clear plot data
		self.plot_frame.axes.plot(self.values)         # plot all data
		self.plot_frame.canvas.draw()
		self.plot_frame.Refresh()
		self.plotting_in_progress = False

# plot window (part of the instrument class)
class instrument_plot_frame(wx.Frame):
	def __init__(self):
		wx.Frame.__init__(self, None, -1, 'Instrument data')
		self.figure = Figure()                                           # create matplotlib figure
		self.axes = self.figure.add_subplot(111)                         # create figure axes
		self.canvas = FigureCanvas(self, -1, self.figure)                # FigureCanvasWxAgg
		self.sizer = wx.BoxSizer(wx.VERTICAL)
		self.sizer.Add(self.canvas, 1, wx.LEFT | wx.TOP | wx.EXPAND)
		self.SetSizer(self.sizer)
		self.Fit()


# 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                 # for communication with the main_window
		self.idle_time = 0.01                          # idle time between instrument readings

	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
			if not self.main_window.instrument.plotting_in_progress:
				wx.CallAfter( self.main_window.instrument.plot_data )  # update the pyplot figure <-- *** THIS NEEDS TO BE IN wx.CallAfter TO AVOID CRASHING ***
			time.sleep(self.idle_time)                                     # 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=(300,150))
		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()