Pausing a GUI Python program

Question

I am trying to create a simple sorting visualizer in python using Tkinter. With that being said, I would like the user to be able to see the changes that occur in each iteration of the sorting algorithm (whatever algorithm is used) and in order to do so, I have to "pause" the program for the user to see the changes each tick.

It's the "pausing" part that confuses me. I looked into time.sleep which is irrelevant for GUI programs (due to the mainloop) and after() in the Tkinter library, but I can't seem to get it right.

My code:

arr = [random.randint(0,600) for i in range(100)]


WIN_WIDTH = 1200
WIN_HEIGHT = 800


BAR_NUM = len(arr)
BAR_WIDTH = WIN_WIDTH // BAR_NUM

class sortVisualizer(tk.Frame):

    def __init__(self, master=None):
        super().__init__(master)
        canvas = tk.Canvas(root,width=WIN_WIDTH,height=WIN_HEIGHT)

        self.draw(canvas)
        canvas.pack()

        queue = [self.bubbleSort(canvas)] //theres going to be more than just one sorting algorithm
        queue[0]

    def re_draw(self,canvas,index1,index2):

        canvas.delete("all")

        temp = arr[index1]
        arr[index1] = arr[index2]
        arr[index2] = temp

        for i in range(BAR_NUM):
            canvas.create_rectangle(BAR_WIDTH * i,
                                    WIN_HEIGHT - arr[i],
                                    BAR_WIDTH * (i+1),
                                    WIN_HEIGHT,
                                    fill = "white")

        canvas.pack()

    def bubbleSort(self,canvas):
        for item in range(len(arr)-1,0,-1):
            for i in range(item):
                if (arr[i] > arr[i+1]):
                    self.re_draw(canvas,i,i+1)

There are a few other functions in the sortVisualizer class but they are irrelevant.

So my question is: how will I be able to "pause" or "stop" the program in order for the user to be see the changes in each tick?

You may not need to actually pause but must update the screen every loop. — Mike - SMT
– Mike - SMT, Commented Sep 7, 2018 at 18:47

Omer Hen · Accepted Answer · 2018-09-07 19:02:15Z

1

Following @Mike - SMT 's comment, I used root.update() at the end of the bubbleSort function as so:

def bubbleSort(self,canvas):
    for item in range(len(arr)-1,0,-1):
        for i in range(item):
            if (arr[i] > arr[i+1]):
                self.re_draw(canvas,i,i+1)
                root.update()

This not only "paused" or "stopped" or showed the progression of the program but also brought up the program's window and allowed for the graphics to be updated from within the mainloop.

answered Sep 7, 2018 at 19:02

Omer Hen

1721 silver badge12 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Mike - SMT Over a year ago

Nice work. Also note that self.draw(canvas) is useless here and in fact causes errors on my end. Also you should use # instead of // in python for comments.

Omer Hen Over a year ago

Thanks. @Mike-SMT, the self.draw(canvas) is another function in my code that I did not include, sorry for leaving that code line there though. Anyways, thanks a lot.

Collectives™ on Stack Overflow

Pausing a GUI Python program

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related