python 3.x - Tkinter, error maximum recursion depth exceeded

Question

I am having trouble writting a tkinter application with matplotlib that updates dinamicaly. I create a plot and use it inside the tkinter window. Then the plot is updated every 50ms with a tk.after() method, which works fine in other applications I have tryed so far. But in my application everything seems to be working until after some time (a minute or so) I get an error:

RecursionError: maximum recursion depth exceeded while calling a Python object

The code is:

import matplotlib
#matplotlib.use('TkAgg')
from numpy import arange, sin, pi
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg, NavigationToolbar2TkAgg
# implement the default mpl key bindings
from matplotlib.backend_bases import key_press_handler
from matplotlib.figure import Figure
import sys
import time

if sys.version_info[0] < 3:
    import Tkinter as Tk
else:
    import tkinter as Tk


import numpy as np
import matplotlib.pyplot as plt
import math

class MainWindow():

    #----------------

    def __init__(self, root):
        self.index=0
        self.root=root
        self.fig, self.ax = plt.subplots()
        self.line, = self.ax.plot(np.random.randn(100))
        #plt.show(block=False)


        # a tk.DrawingArea
        self.canvas = FigureCanvasTkAgg(self.fig, master=root)
        self.canvas.show()
        self.canvas.get_tk_widget().pack(side=Tk.TOP, fill=Tk.BOTH, expand=1)

        self.toolbar = NavigationToolbar2TkAgg(self.canvas, root)
        self.toolbar.update()
        self.canvas._tkcanvas.pack(side=Tk.TOP, fill=Tk.BOTH, expand=1)


        self.canvas.mpl_connect('key_press_event', self.on_key_event)

        self.display = Tk.Label(root, text="") # we need this Label as a variable!
        self.display.pack()

        self.button1 = Tk.Button(master=root, text='Quit', command=self._quit)
        self.button1.pack(side=Tk.BOTTOM)

        global w
        w=2*math.pi


        self.button2 = Tk.Button(master=root, text='Increase frecuency', command=self.button2_event)
        self.button2.pack(side=Tk.BOTTOM)

        #A simple clock
        global miliseconds
        global t
        t=time.time()
        self.update_clock()
        print('going to the next stop')
        self.root.mainloop()


    def on_key_event(event):
        print('you pressed %s' % event.key)
        key_press_handler(event, self.canvas, toolbar)




    def _quit(self):
        self.root.quit()     # stops mainloop
        self.root.destroy()  # this is necessary on Windows to prevent
                        # Fatal Python Error: PyEval_RestoreThread: NULL tstate

    def button2_event(self):

        global t
        global w
        w+=2*3.1416

    def update_clock(self):

        global t
        mili=str(math.floor(1000*(t-time.time())))+' ms'
        t=time.time()


        now = time.strftime("%H:%M:%S"+'-'+mili)
        self.display.configure(text=now)

        N=100
        y=np.sin(4*math.pi*(np.array(range(N))/N)+t*w)
        x=range(N)
        self.line.set_ydata(y)
        self.line.set_xdata(x)

        self.ax.relim()
        self.ax.autoscale()
        #?fig.canvas.update()
        #fig.canvas.flush_events()

        self.canvas.show()
        self.canvas.flush_events()

        self.root.after(50, self.update_clock()) #<------ERROR HERE!------


root = Tk.Tk()
root.wm_title("Embedding in TK")
MainWindow(root)

Answer 1

Change self.root.after(50, self.update_clock()) to self.root.after(50, self.update_clock), after

after(delay_ms, callback=None, *args)

Registers an alarm callback that is called after a given time.