How to make canvas objects and delete them in PySimpleGUI?

Python Help
1

I made a program where the MakeRect function makes a rectangle at specified parameters and the DeleteObj function deletes the last one added, and it looks like the code works. However, the DeleteObj function wont work against the rectangles added by the MakeRect function, because the list insertion somehow gets wrong, I do not know why. When I call the MakeRect function It is supposed to be from [0, 1] to [0, 1, 2] and finally [0, 1, 2, 3] and when I call the DeleteObj function, it goes from [0, 1, 2, 3] to [0, 1, 2] and so on. Instead, I get [1, 0], [2, 0], [3, 0] and so on, and when I call the DeleteObj function, it goes back to just [], and when I activate the MakeRect function again, it instantly goes to [4.0] and so on. Can somebody help me? Here’s the code:

import PySimpleGUI as sg

sg.theme('DefaultNoMoreNagging')

items_files = [  [sg.Button(pad = (0, 0), tooltip = 'Delete from Frontmost', key = 'DelF')]  ]

tab2 = [  [sg.Button(key = 'Rect', pad = (0, 0), tooltip = 'Rectangle')]  ]

BC = 'white'
CW = 600
CH = 450
LXM = (CW / 2)
LYM = (CH / 2)

mid_left = [  [sg.Text(text = "X:"), sg.Input(default_text = "0", key = "TLX", size = (3, 1))],
              [sg.Text(text = "Y:"), sg.Input(default_text = "0", key = "TLY", size = (3, 1))],
              [sg.Text(text = "Scale X:"), sg.Input(default_text = "0", key = "TSX", size = (3, 1))],
              [sg.Text(text = "Scale Y:"), sg.Input(default_text = "0", key = "TSY", size = (3, 1))]  ]

can = sg.Canvas(size = (CW, CH), background_color = BC, border_width = 1, key = "canvas")

mid_screen = [  [sg.Frame("Insert Values", mid_left, expand_x = True, expand_y = True), can]  ]

layout = [  [sg.Frame("", items_files, pad = (1, 1), expand_x = False, expand_y = False), sg.TabGroup([[sg.Tab('Insert', tab2)]])],
            [mid_screen]  ]
window = sg.Window('title', layout, finalize = True)
tkc = can.TKCanvas
while True:
    event, values = window.read()
    N = 0

    OL = [0]

    TLX = values["TLX"]
    TLY = values["TLY"]
    TSX = values["TSX"]
    TSY = values["TSY"]
    LT = 1
    FC = 'red'
    LC = 'black'

    def MakeRect():
        pum = N
        OL.insert(pum, tkc.create_rectangle((float(LXM) + float(TLX) + float(TSX)), (float(LYM) + float(TLY) + float(TSY)), (float(LXM) + float(TLX) - float(TSX)), (float(LYM) + float(TLY) - float(TSY)), fill = FC, outline = LC, width = LT,  tag = pum))
        pum = N + 1
        return pum

    def DeleteObj():
        pum = N
        tkc.delete(OL[pum])
        del OL[pum]
        pum = N - 1

    if event == 'Rect':
        MakeRect()
        print (OL)
        print (N)

    if event == 'DelF':
        DeleteObj()
        print (OL)
        print (N)
    
    if event in (sg.WIN_CLOSED, 'Exit'):
        break

window.close()

P.S. Bonus points if you can solve the TypeError: 'NoneType' object is not subscriptable error. Full:

Traceback (most recent call last):
  File "C:\Users\User\AppData\Local\Programs\Python\Python311\Help.py", line 34, in <module>
    TLX = values["TLX"]
TypeError: 'NoneType' object is not subscriptable
2

When you create a rectangle, you’re storing its ID in OL, but you have OL = [0] in the loop, which will reset it each time.

As for the exception, it’s because window.read() returns (None, None) when you close the window.

3

Thanks Barnett, but I am still not able to diagnose and stop this error, since it comes from variables that have specific values from entries assigned.

What should I do to stop this error from happening again?