Binding event to combobox selection to display image inside Toplevel window (Tkinter Python)

I am attempting to bind a selection event to items within a combobox to display an image inside a toplevel window once the specified item is selected. The code I have runs without error. However, the images are not displayed upon selecting the items inside the combobox. Any help would be appreciated.

from tkinter import *
import tkinter as tk
from tkinter import ttk

class Image_viewer:

    def __init__(self, win):
        self.root = win
        self.root.title('Root Window')
        self.root.geometry('200x150+600+200')

        self.lblHeading = tk.Label(self.root,
                                   text = 'Root Window',
                                   font = ('Times New Roman', 14),
                                   bg = 'White')
        self.lblHeading.pack(side = tk.TOP)
        self.lblHeading.focus()

        self.btnView = tk.Button(self.root, text = 'Image Viewer', command = self.view)
        self.btnView.place(relx = 0.5, rely = 0.9, anchor = tk.SE)
        self.btnClose = tk.Button(self.root, text = 'Close', command = self.close)
        self.btnClose.place(relx = 0.8, rely = 0.9, anchor = tk.SE)
    def CMBinsert(self):
        self.imgas = tk.PhotoImage(file = '../raw/as.png')
        self.imggr = tk.PhotoImage(file = '../raw/gr.png')
        if self.box_value.get() == 'as':
                #creates textbox to insert image into 
                self.mytext = tk.Text(self.top)
                self.mytext.place(relx = 0.5, rely = 0.80, height=150, width=200, anchor = tk.CENTER)
                #inserts image into textbox
                self.mytext.image_create(tk.END, image = self.imgas)
        elif self.box_value.get() == 'gr':
                #creates textbox to insert image into 
                self.mytext = tk.Text(self.top)
                self.mytext.place(relx = 0.5, rely = 0.80, height=150, width=200, anchor = tk.CENTER)
                #inserts image into textbox
                self.mytext.image_create(tk.END, image = self.imgas)
        else:
            pass  
    def view(self):
        #creating top level
        self.top = Toplevel()
        self.top.title('Top Level')
        self.top.geometry('500x500')
        #Quit Button
        self.btnClose2 = Button(self.top, text="Quit", command= self.top.destroy)
        self.btnClose2.place(relx = 0.9, rely = 0.1, anchor = tk.SE)
        #initializing combobox
        self.box_value=StringVar()
        self.CMB = ttk.Combobox(self.top, textvariable=self.box_value, state='readonly')
        self.CMB['values']=['as','gr']
        self.CMB.place(relx = 0.6, rely = 0.3, anchor = tk.SE)
        #binding selection event to combobox selection event
        self.CMB.bind("<<ComboboxSelected>>", self.CMBinsert())
    def close(self):
        self.root.destroy()

def main():
    root = tk.Tk()
    Image_viewer(root)
    root.mainloop()

if __name__ == '__main__':
    main()

Answer

This is a subtle issue with binding the callback to the Combobox event, you need to pass in a function as an argument, but you wrote

self.CMB.bind("<<ComboboxSelected>>", self.CMBinsert())

with the parenthesis after self.CMBinsert, so you’re not passing the function, you’re actually calling the function once, and passing in the result instead. Just remove those parenthesis:

self.CMB.bind("<<ComboboxSelected>>", self.CMBinsert)

After that, you get an error on the callback’s signature:

TypeError: CMBinsert() takes 1 positional argument but 2 were given

because it’s expecting an event parameter, just change your def to:

 def CMBinsert(self, evt):