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Hide & Remove,Come Back!,

 Hide & Remove


DISCLAIMER: I promise the good stuff is coming back. We have to go through the valley to get to the mountain, right?
Sometimes, we want to remove a button, image or piece of text from the screen.
To do this, we use pack_forget().


👉 We'll start with our default tkinter program.


import tkinter as tk
window = tk.Tk()
window.title("Hello World") 
window.geometry("300x200") 
hello = tk.Label(text = "Hello World") 
hello.pack() 
button = tk.Button(text = "Click me!") 
button.pack()
tk.mainloop()

👉 Now I'm going to add a new subroutine to hide the label and call it on a button click.


import tkinter as tk
window = tk.Tk()
window.title("Hello World") 
window.geometry("300x200") 
# New subroutine
def hideLabel():
  hello.pack_forget() # Removes the 'hello' label
hello = tk.Label(text = "Hello World") 
hello.pack() 
button = tk.Button(text = "Click me!", command = hideLabel) # Calls the 'hideLabel' sub on click.
button.pack()
tk.mainloop()

👉 Let's look at the window after this code runs:


Come Back!

To bring the label back, we use a Boolean variable to store the state of the label. Is it 'on' (True) or 'off' (False)? The variable starts as True.
I'll add this variable to the hideLabel sub as a global, and set it to 'False' when the sub is called.
Now I can use selection in the hideLabel sub to check the value in labelOn. If it's 'True' I'll hide the label, if it's 'False', I'll show the label.


import tkinter as tk
window = tk.Tk()
window.title("Hello World") 
window.geometry("300x200") 
labelOn = True
def hideLabel():
  global labelOn
  if labelOn: # if labelOn is Python shorthand for 'if labelOn == True'
    hello.pack_forget()
    labelOn = False
  else:
    hello.pack()
    labelOn = True
hello = tk.Label(text = "Hello World") 
hello.pack() 
button = tk.Button(text = "Click me!", command = hideLabel) 
button.pack()
tk.mainloop()

Try it out. The button should now toggle the label from visible to invisible.
👉 It will spawn underneath the button though, so we'll need to control where it loads.
I can do this by hiding and respawning everything in the correct order in the else part of the selection.


def hideLabel():
  global labelOn
  if labelOn: 
    hello.pack_forget()
    labelOn = False
  else:
    button.pack_forget #hides the button
    hello.pack() # shows the label first (top of the window)
    button.pack() # then reloads the button underneath
    labelOn = True
Hiding Images
Here's our image code from Day 67.
import tkinter as tk
window = tk.Tk()
window.title("Hello World") 
window.geometry("300x200") 
def changeImage():
  canvas.itemconfig(container, image = newImage)
hello = tk.Label(text = "Hello World") 
hello.pack() 
button = tk.Button(text = "Click me!", command=changeImage) 
button.pack()

canvas = tk.Canvas(window, width = 300, height=150) 
canvas.pack()
image = tk.PhotoImage(file="theFeels.png") 
image = image.subsample(5)
newImage = tk.PhotoImage(file="success.png") 
newImage = newImage.subsample(5) 
container = canvas.create_image(150,1,image=image) 
tk.mainloop()


👉 I'm going to add a second button called 'button2' that will hide the image. Actually, what we're really doing is hiding the canvas. Here's the isolated code for that.


button2 = tk.Button(text = "Hide Image!", command=hideImage) 
button2.pack()


👉 Next I need to create the hideImage sub above the button creation. The isolated code is:


def hideImage():
  canvas.pack_forget()

👉 Now, here are those code snippets as part of the whole program:


import tkinter as tk
window = tk.Tk()
window.title("Hello World") 
window.geometry("300x200") 
def changeImage():
  canvas.itemconfig(container, image = newImage)
#### NEW SUBROUTINE ######
def hideImage():
  canvas.pack_forget()
hello = tk.Label(text = "Hello World") 
hello.pack() 
button = tk.Button(text = "Click me!", command=changeImage) 
button.pack()
#### NEW BUTTON ######
button2 = tk.Button(text = "Hide Image!", command=hideImage) 
button2.pack()
canvas = tk.Canvas(window, width = 300, height=150) 
canvas.pack()
image = tk.PhotoImage(file="theFeels.png") 
image = image.subsample(5)
newImage = tk.PhotoImage(file="success.png") 
newImage = newImage.subsample(5) 
container = canvas.create_image(150,1,image=image) 
tk.mainloop()










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