How to avoid infinte loop

Question

How can I avoid this while True Loop. I have to run def func(i) infinite times. The reason for avoiding this while True loop is that whenever I create two classes, one class having this piece of code and another class having a button to access this piece of code when button is pressed, but the problem I get is that I cannot integrate this matplotlib within the tkinter window. The button is shown separately and the matplotlib is running separately. But when I remove while loop then it somehow solves the problem but then there is no infinite loop.

import matplotlib
matplotlib.use("TkAgg")
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg
import matplotlib.pyplot as plt
import numpy as np
import tkinter as tk
from tkinter import *
import matplotlib.animation as animation

j=0
fig = plt.figure()
ax1 = fig.add_axes([0.85, 0.093, 0.04, 0.8])
cax = fig.add_subplot(1, 1, 1)

H = np.array([[1, 2, 3, 1], [4, 5, 6, 10], [3, 7, 8, 4], [10, 5, 3, 1]])
Z = np.array([[3, 290, 600], [1011, 230, 830], [152, 750, 5]])

while True:
    def func(i):
        global j
        if j == 0:
            j += 1
            rows, cols = H.shape

            im = plt.imshow(H, interpolation='nearest',
                            extent=[0, cols, 0, rows],
                            cmap='bwr', vmin=0, vmax=10)
            fig.colorbar(im, cax=ax1, orientation='vertical')


        elif j == 1:

            j -= 1
            rows, cols = H.shape

            im = plt.imshow(Z, interpolation='nearest', cmap='Spectral', vmin=0, vmax=1023,extent=[0, cols, 0, rows])
            v = np.linspace(0, 1023, 15, endpoint=True)
            fig.colorbar(im, cax=ax1, orientation='vertical', ticks=v)


    ani = animation.FuncAnimation(fig, func, interval=1000)
    plt.show()
    plt.close()

Answer 1

Code style: can you avoid running the def repeatedly by instead defining two functions, func0(i) for the j==0 case and func1(i) for the j==1 case? (I assume func has to have a predefined signature and you can't add j as a parameter to it.) And then change the body of the infinite loop to

ani = animation.FuncAnimation(fig, func0, interval=1000)
plt.show()
plt.close()
ani = animation.FuncAnimation(fig, func1, interval=1000)
plt.show()
plt.close()

Use a timer or a thread instead: it's a bad idea to have infinite loops in a GUI app, at least in the thread that's processing events. Can you put the infinite loop into a separate thread (caution, threads are not for the faint-hearted) or change it into a repeating timer-driven event (with no loop in the event)?

More on timers: The idea is to use a timer to run one loop, then return to the GUI so it gets updated and is responsive. Tkinter supports timers using the after() method of the root window. I don't know if it supports repeating timers but all you have to do is restart the timer at the end of your timer event.

There are some examples in How to create a timer using tkinter?, How to create a timer using tkinter? and Python - Countdown timer within a tkinter canvas.

_{(Sorry, I would have preferred to add this as a comment but I don't have enough reputation here.)}