I'm just starting with python and i'm having a problem. I've tried various solutions, but i can't update the field that says '19'. When i click on plus, i want it to be 20, then 21,... and when i click - it has to go back to 20 , 19. Can anybody tell me how to solve this?

 from tkinter import *def fct_tempplus():while True:#  tekstvak_input_user = tekstvak_input_user +1return tekstvak_input_user + 1def fct_tempmin():print ('ok')window = Tk()window.geometry("800x400")  # not *window.title("TEST")label= Label( window, text = "Temp?")label.place(x=350,y=175)tempplus=Button(window, bd=10,width=10, height = 1,text="+",command=fct_tempplus,
font=("Helvetica", 12))tempplus.place(x=500,y=150)tempmin=Button(window, bd=10,width=10, height = 1,text="-", font=("Helvetica", 12),command=fct_tempmin)tempmin.place(x=500,y=200)tekstvak_input_user = Entry(window, width = 10 )tekstvak_input_user.insert(0,19.0)tekstvak_input_user.place(x=350 , y=200)window.mainloop()`

while True is not needed in this program. And you have to use .get() to get a value inside a function. And then you should store it in a globalized variable, convert it into int or float. Then, simply use delete(0, END) to clear what's inside the Entry widget and then use insert() to insert the new value in the Entry.

Like This:

from tkinter import *var = 0def fct_temp_plus():global varvar = float(tekstvak_input_user.get())var += 1tekstvak_input_user.delete(0, END)tekstvak_input_user.insert(0, var)def fct_temp_min():global varvar = float(tekstvak_input_user.get())var -= 1tekstvak_input_user.delete(0, END)tekstvak_input_user.insert(0, var)window = Tk()
window.geometry("800x400")  # not *
window.title("TEST")label = Label(window, text="Temp?")
label.place(x=350, y=175)temp_plus = Button(window, bd=10, width=10, height=1, text="+", command=fct_temp_plus, font=("Helvetica", 12))
temp_plus.place(x=500, y=150)temp_min = Button(window, bd=10, width=10, height=1, text="-", font=("Helvetica", 12), command=fct_temp_min)
temp_min.place(x=500, y=200)tekstvak_input_user = Entry(window, width=10)
tekstvak_input_user.insert(0, 19.0)
tekstvak_input_user.place(x=350, y=200)window.mainloop()

Note: You should always import tkinter as tk.

Like This:

import tkinter as tkvar = 0def fct_temp_plus():global varvar = float(tekstvak_input_user.get())var += 1tekstvak_input_user.delete(0, tk.END)tekstvak_input_user.insert(0, var)def fct_temp_min():global varvar = float(tekstvak_input_user.get())var -= 1tekstvak_input_user.delete(0, tk.END)tekstvak_input_user.insert(0, var)window = tk.Tk()
window.geometry("800x400")
window.title("TEST")label = tk.Label(window, text="Temp?")
label.place(x=350, y=175)temp_plus = tk.Button(window, bd=10, width=10, height=1, text="+", command=fct_temp_plus, font=("Helvetica", 12))
temp_plus.place(x=500, y=150)temp_min = tk.Button(window, bd=10, width=10, height=1, text="-", font=("Helvetica", 12), command=fct_temp_min)
temp_min.place(x=500, y=200)tekstvak_input_user = tk.Entry(window, width=10)
tekstvak_input_user.insert(0, 19.0)
tekstvak_input_user.place(x=350, y=200)window.mainloop()