update matplotlib plot in tkinter GUI

Question

I wanna update a matplotlib plot in a tkinter GUI. I tried to do so in the following code example.

import matplotlib
matplotlib.use('TkAgg')
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg, NavigationToolbar2TkAgg
from matplotlib.figure import Figure
import tkinter as tk
import tkinter.ttk as ttk
import sys
class Application(tk.Frame):
 def __init__(self, master=None):
 tk.Frame.__init__(self,master)
 self.createWidgets()
 def createWidgets(self):
 fig=plt.figure(figsize=(8,8))
 ax=fig.add_axes([0.1,0.1,0.8,0.8],polar=True)
 canvas=FigureCanvasTkAgg(fig,master=root)
 canvas.get_tk_widget().grid(row=0,column=1)
 canvas.show()
 self.plotbutton=tk.Button(master=root, text="plot", command=self.plot)
 self.plotbutton.grid(row=0,column=0)
 def plot(self):
 for line in sys.stdout: #infinite loop, reads data of a subprocess
 theta=line[1]
 r=line[2]
 ax.plot(theta,r,linestyle="None",maker='o')
 plt.show(block=False)
 plt.pause(0.001)
 plt.cla()
 #here set axes
root=tk.Tk()
app=Application(master=root)
app.mainloop()

At the moment the problem is, that the ax object is not known in the plot function. If I try plot(self,canvas,ax) the GUI does not open. Only a figure that plots the data.

I wanna plot the data in the figure that is seen in the GUI. At least with a refresh rate round about 3-5Hz. Cause I am an absolute beginner this code solution is probably not the best way to do so. So I would be happy, if someone could show me a smarter solution.

Thanks!

Answer 1

Ok I could solve it myself. Here the solution:

import matplotlib
matplotlib.use('TkAgg')
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg, NavigationToolbar2TkAgg
from matplotlib.figure import Figure
import tkinter as tk
import tkinter.ttk as ttk
import sys
class Application(tk.Frame):
 def __init__(self, master=None):
 tk.Frame.__init__(self,master)
 self.createWidgets()
 def createWidgets(self):
 fig=plt.figure(figsize=(8,8))
 ax=fig.add_axes([0.1,0.1,0.8,0.8],polar=True)
 canvas=FigureCanvasTkAgg(fig,master=root)
 canvas.get_tk_widget().grid(row=0,column=1)
 canvas.show()
 self.plotbutton=tk.Button(master=root, text="plot", command=lambda: self.plot(canvas,ax))
 self.plotbutton.grid(row=0,column=0)
 def plot(self,canvas,ax):
 for line in sys.stdout: #infinite loop, reads data of a subprocess
 theta=line[1]
 r=line[2]
 ax.plot(theta,r,linestyle="None",maker='o')
 canvas.draw()
 ax.clear()
 #here set axes
root=tk.Tk()
app=Application(master=root)
app.mainloop()

Answer 2

Thanks Abishek for taking the time to post the answer to your own problem.

I've just modified your answer a bit so that it runs as a standalone module without needing input from sys.stdout. Also changed the tkinter imports for python 2.7

import matplotlib
matplotlib.use('TkAgg')
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg, NavigationToolbar2TkAgg
from matplotlib.figure import Figure
import Tkinter as tk # python 2.7
import ttk # python 2.7
import sys
class Application(tk.Frame):
 def __init__(self, master=None):
 tk.Frame.__init__(self,master)
 self.createWidgets()
 def createWidgets(self):
 fig=plt.figure(figsize=(8,8))
 ax=fig.add_axes([0.1,0.1,0.8,0.8],polar=True)
 canvas=FigureCanvasTkAgg(fig,master=root)
 canvas.get_tk_widget().grid(row=0,column=1)
 canvas.show()
 self.plotbutton=tk.Button(master=root, text="plot", command=lambda: self.plot(canvas,ax))
 self.plotbutton.grid(row=0,column=0)
 def plot(self,canvas,ax):
 c = ['r','b','g'] # plot marker colors
 ax.clear() # clear axes from previous plot
 for i in range(3):
 theta = np.random.uniform(0,360,10)
 r = np.random.uniform(0,1,10)
 ax.plot(theta,r,linestyle="None",marker='o', color=c[i])
 canvas.draw()
root=tk.Tk()
app=Application(master=root)
app.mainloop()

Answer 3

I don't know if it will be useful to anybody, but I updated the code to run with matplotlib 3.1.x+ and python 3.

import matplotlib.pyplot as plt
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg
import tkinter as tk 
import numpy as np
class Application(tk.Frame):
 def __init__(self, master=None):
 tk.Frame.__init__(self,master)
 self.createWidgets()
 def createWidgets(self):
 fig=plt.figure(figsize=(8,8))
 ax=fig.add_axes([0.1,0.1,0.8,0.8],polar=True)
 canvas=FigureCanvasTkAgg(fig,master=root)
 canvas.get_tk_widget().grid(row=0,column=1)
 canvas.draw()
 self.plotbutton=tk.Button(master=root, text="plot", command=lambda: self.plot(canvas,ax))
 self.plotbutton.grid(row=0,column=0)
 def plot(self,canvas,ax):
 c = ['r','b','g'] # plot marker colors
 ax.clear() # clear axes from previous plot
 for i in range(3):
 theta = np.random.uniform(0,360,10)
 r = np.random.uniform(0,1,10)
 ax.plot(theta,r,linestyle="None",marker='o', color=c[i])
 canvas.draw()
root=tk.Tk()
app=Application(master=root)
app.mainloop()

Answer 4

With 3 extra code lines can animate the plot updates. To highlight the essence, I simplified the code by removing some pieces (like 'master=') related to multi-instance cases.

import matplotlib.pyplot as plt
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg
import tkinter as tk
import numpy as np
class Application(tk.Tk):
 def __init__(self):
 super().__init__()
 self.create_widgets()
 def create_widgets(self):
 fig = plt.figure(figsize=(8, 8))
 ax = plt.axes((0.1, 0.1, 0.8, 0.8), polar=True)
 canvas = FigureCanvasTkAgg(fig, self)
 canvas.get_tk_widget().grid(row=0, column=1)
 plotbutton = tk.Button(self, text="plot", command=lambda: self.auto_plot(ax))
 plotbutton.grid(row=0, column=0)
 def auto_plot(self, ax):
 c = ['r', 'b', 'g']
 for j in range(5):
 ax.clear()
 for i in range(3):
 theta = np.random.uniform(0, 360, 10)
 r = np.random.uniform(0, 1, 10)
 plt.polar(theta, r, linestyle="None", marker='o', color=c[i])
 plt.draw()
 self.after(500) # display plot keeping button responsive
 self.update() # redraw plot
Application().mainloop()