update plot by a button click on tkinter python

Question

I am using tkinter in python. I would like to be able to plot data as I click on the button compute. and also I would like also to take into account the values given in the entries. Up to now my script run normally, but nothing happen when I click compute of change the entry values. here is the code :

#------- start
from tkinter import *
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg
from matplotlib.figure import Figure
import matplotlib
matplotlib.use("TkAgg")
import matplotlib.pyplot as plt
import numpy as np
class MyWindow:
 def __init__(self, win):
 x0, xt0, y0 = 10, 100, 50
 #---- First label and entry -------
 self.lbl0 = Label(win, text='Initial instant')
 self.lbl0.config(font=('Arial', 9))
 self.lbl0.place(x=x0, y=y0)
 self.t0 = Entry()
 self.t0.place(x=xt0, y=y0)
 self.t0.insert(END, str(0))
 self.t_0 = float(self.t0.get())
 #---- Second label and entry -------
 self.lbl1 = Label(win, text='Final instant')
 self.lbl1.config(font=('Arial', 10))
 self.lbl1.place(x=x0, y=y0 + 40)
 self.t1 = Entry()
 self.t1.place(x=xt0, y=y0 + 40)
 self.t1.insert(END, str(1))
 self.t_1 = float(self.t1.get())
 #---- Compute button -------
 self.btn = Button(win, text='Compute')
 self.btn.bind('<Button-1>', self.plot)
 self.btn.place(x=xt0, y=y0 + 80)
 self.figure = Figure(figsize=(4.5, 3), dpi=100)
 #---- subplot 1 -------
 self.subplot1 = self.figure.add_subplot(211)
 self.subplot1.set_xlim(self.t_0, self.t_1)
 #---- subplot 2 -------
 self.subplot2 = self.figure.add_subplot(212)
 self.subplot2.set_xlabel('$Time(s)$', fontsize=11)
 self.subplot2.set_xlim(self.t_0, self.t_1)
 #---- Show the plot-------
 self.plots = FigureCanvasTkAgg(self.figure, win)
 self.plots.get_tk_widget().pack(side=RIGHT, fill=BOTH, expand=0)
 def data(self):
 self.t_0 = float(self.t0.get())
 self.t_1 = float(self.t1.get())
 t = np.linspace(self.t_0, self.t_1, 100)
 func1 = t**0.5
 func2 = t**2.
 return t, func1, func2
 def plot(self, event):
 t, func1, func2 = self.data()
 self.t_0 = float(self.t0.get())
 self.t_1 = float(self.t1.get())
 self.subplot1.set_xlim(self.t_0, self.t_1)
 self.subplot1.plot(t, func1, 'r', lw=2.5)
 self.subplot2.set_xlim(self.t_0, self.t_1)
 self.subplot2.plot(t, func2, 'b', lw=2.5)
window = Tk()
mywin = MyWindow(window)
window.title('My model')
window.geometry("800x600+10+10")
window.mainloop()

Answer 1

You were missing a small detail in your MyWindow.plot() method, and it is to actually draw your plots. If you modify it like this (note the additional line in the function):

def plot(self, event):
 t, func1, func2 = self.data()
 self.t_0 = float(self.t0.get())
 self.t_1 = float(self.t1.get())
 self.subplot1.set_xlim(self.t_0, self.t_1)
 self.subplot1.plot(t, func1, 'r', lw=2.5)
 self.subplot2.set_xlim(self.t_0, self.t_1)
 self.subplot2.plot(t, func2, 'b', lw=2.5)
 self.plots.draw()

Then you get the expected behavior (for the default case in this example):

enter image description here

• user3733333: Thank you that works pretty find ^^ ! How can I clear the plots before adding a new one ?
• panadestein: @user3733333 no problem. You can get more information about clearing the plots in this post. A quick and dirty way of doing it might be to use draw again with empty lists.

Answer 2

In order to clear the plots before adding a new one, you can use :

your_fig.clf() (clears the figure)

or

your_fig.cla() (clears the axis).

or

ax.clear()

:)