Change position of label in Tkinter window

Question

I am writing a simple program that pulls up an image (BackgroundFinal.png) and displays it in a window. I want to be able to press a button on the window to move the picture down by 22 pixels. Everything works except the button does not do anything.

import Tkinter
import Image, ImageTk
from Tkinter import Button


a = 0       #sets inital global 'a' and 'b' values
b = 0

def movedown():             #changes global 'b' value (adding 22)
    globals()[b] = 22
    return

def window():               #creates a window 
    window = Tkinter.Tk();
    window.geometry('704x528+100+100');

    image = Image.open('BackgroundFinal.png');      #gets image (also changes image size)
    image = image.resize((704, 528));
    imageFinal = ImageTk.PhotoImage(image);

    label = Tkinter.Label(window, image = imageFinal);   #creates label for image on window 
    label.pack();
    label.place(x = a, y = b);      #sets location of label/image using variables 'a' and 'b'

    buttonup = Button(window, text = 'down', width = 5, command = movedown()); #creates button which is runs movedown()
    buttonup.pack(side='bottom', padx = 5, pady = 5);

    window.mainloop();

window()

If I am not mistaken, the button should change the global 'b' value, therefore changing the y position of the label. I really appreciate any help, sorry for my god-awful conventions. Thanks in advance!

Answer 1

You have a few problems here.

First, you're using pack and place . In general, you should only use 1 geometry manager within a container widget. I don't recommend using place . That's just too much work that you need to manage.

Second, you're calling the callback movedown when you construct your button. That's not what you want to do -- You want to pass the function, not the result of the function:

buttonup = Button(window, text = 'down', width = 5, command = movedown)

Third, globals returns a dictionary of the current namespace -- It's not likely to have an integer key in it. To get the reference to the object referenced by b , you'd need globals()["b"] . Even if it did, changing the value of b in the global namespace won't change the position of your label because the label has no way of knowing that change. And in general, if you need to use globals , you probably need to rethink your design.

Here's a simple example of how I would do it...

import Tkinter as tk

def window(root):
    buf_frame = tk.Frame(root,height=0)
    buf_frame.pack(side='top')
    label = tk.Label(root,text="Hello World")
    label.pack(side='top')
    def movedown():
        buf_frame.config(height=buf_frame['height']+22)

    button = tk.Button(root,text='Push',command=movedown)
    button.pack(side='top')

root = tk.Tk()
window(root)
root.mainloop()

Answer 2

Thanks for the reply but, It was not really what I was looking for. I'll post what I found worked best here for anybody else with the same problem.

Essentially, It is much better, in this case, to use a Canvas instead of a label. With canvases, you can move objects with canvas.move, here is a simple example program

# Python 2
from Tkinter import *

# For Python 3 use:
#from tkinter import *

root = Tk()
root.geometry('500x500+100+100')

image1 = PhotoImage(file = 'Image.gif')

canvas = Canvas(root, width = 500, height = 400, bg = 'white')
canvas.pack()
imageFinal = canvas.create_image(300, 300, image = image1)

def move():
    canvas.move(imageFinal, 0, 22)  
    canvas.update()

button = Button(text = 'move', height = 3, width = 10, command = move)
button.pack(side = 'bottom', padx = 5, pady = 5)

root.mainloop()

my code may not be perfect (sorry!) but that is the basic idea. Hope I help anybody else with this problem