Check if widget exist(Tkinter)

Question

I'd like to check if a widget (such as rectangle drawn on a canvas) exists before I delete it.

Here's my problem: I have two methods that delete rectangles. One is bound to button-1 using bind (delete the rectangle when it is clicked) and the other method deletes a rectangle if it doesn't get clicked in a certain amount of time (checked using Widget.after). I would like to check if the rectangle exists in the second method because I want to count the rectangles user didn't click and the only way I can think of is check if it is already deleted. Is there a way to do this? Of course, I could set a variable inside button-1 event handler and check it from the other method. But just wanted to know if Tkinter provides method such as "item exist".

Edit : Well, I just found out one trick. If I use itemconfig on deleted widget, I get empty set. I use that value to see if a widget is already deleted or not. I'm not sure if it's an elegant way to do it though.

mgilson · Accepted Answer · 2012-11-01 19:07:35Z

5

It looks to me that you could use Canvas.find_all to get a tuple of all of the items on your canvas. Then you could see if your particular item is in that tuple. e.g.:

if item in my_canvas.find_all():
   my_canvas.delete(item)
else:
   print("Item not on canvas")

answered Nov 1, 2012 at 19:07

mgilson

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drchicken · Accepted Answer · 2023-04-27 17:15:08Z

0

You can also unmap the widget with forget instead of destroying it so that the widget disappears but the variable name stays valid. widget.winfo_ismapped() will tell you if it is mapped.

>>> root = tk.Tk()
>>> widget = tk.Label(root, text='squeamish ossifrage')
>>> widget.winfo_ismapped()
0
>>> widget.pack()
>>> widget.winfo_ismapped()
1
>>> widget.forget()
>>> widget.winfo_ismapped()
0

There is no problem running widget.forget() on an unmapped widget so you don't even need to check its status for future statements; just run forget or run pack or overwrite the variable as needed.

answered Apr 27, 2023 at 17:15

drchicken

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