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

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()

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

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()