Python - Tkinter - Finding the loop

Question

Once again I am stucked.

In a canvas I display 9 images Every 8 rows I add a column. This is only for testing purposes. At the end the images should be hundreds. I am trying to identify each image with a unique number. In order to do this I have an event which gives me the coordinates of the canvas. And here comes the noobs part. To get this unique number my code is

 if x_on_grid==0 and y_on_grid==448:
        index_bin=0
    elif x_on_grid==0 and y_on_grid==384:
        index_bin=1
    elif x_on_grid==0 and y_on_grid==320:
        index_bin=2
    elif x_on_grid==0 and y_on_grid==256:
        index_bin=3
    elif x_on_grid==0 and y_on_grid==192:
        index_bin=4
    elif x_on_grid==0 and y_on_grid==128:
        index_bin=5
    elif x_on_grid==0 and y_on_grid==64:
        index_bin=6
    elif x_on_grid==0 and y_on_grid==0:
        index_bin=7
    elif x_on_grid==64 and y_on_grid==448: #new column
        index_bin=8
    elif x_on_grid==64 and y_on_grid==384:
        index_bin=9

Of course it works perfectly, but it's not scientific at all. I am trying to reduce all these lines with a loop but I can't get the number needed, only the last one.

Any ideas?

Best

just so You know but using canvas.create_stuff returns an id. so basically say image1 = canvas.create_image(*args, **kwargs) will result in image1 being an integer for example 1 so there is no need to do what You are doing — Matiiss
– Matiiss, Commented May 17, 2021 at 10:21
Something like index_bin = (448 - y_on_grid) // 64 + 8 * (x_on_grid // 64) - you might want to replace some constants by variables to accomodate more images. — Thierry Lathuille
– Thierry Lathuille, Commented May 17, 2021 at 10:24
I'd use tags. When you create an object you can add a tag to it as an identifier. use something like image-001. When the user clicks, use the canvas find_closest method to determine which object you clicked on and get the object's tag to find out what it's index is. — scotty3785
– scotty3785, Commented May 17, 2021 at 14:08

scotty3785 · Accepted Answer · 2021-05-17 14:25:32Z

Consider the following code

import tkinter as tk

def onclick(event):
    print(vars(event))
    nearest = event.widget.find_closest(event.x,event.y)
    nearest_tag = event.widget.gettags(nearest)[0]
    print(nearest_tag)

def drawCircles(c):
    size = 20
    for i in range(100):
        row = i % 10
        col = i // 10
        x1 = (row * size) + 30
        y1 = (col * size) + 30
        c.create_oval((x1,y1,x1+size,y1+size),tags="image_%03d" % i)

root = tk.Tk()
c = tk.Canvas(root,width=400,height=400,bg="white")
c.grid()
c.bind("<Button-1>",onclick)

drawCircles(c)
root.mainloop()

I'm using circles(ovals) rather than images but the principle is still the same. I draw 100 circles and as I draw then I assign a tag to them in the format image_?. When I click on the canvas, the find_closest method is used to determine which of the circles is nearest to the click. It then looks up the tag (or tags) of that object and prints it out.

No need for long winded if-elif-else statements.

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