Create entries and checkboxes based on items in a list

Question

here is a section of a tkinter app I am working on, and I need to take an input of a list, and use that to create a window with an entry and checkbox for every item in the list. When the checkbox is clicked, I want to fill in the corresponding entry with a default value. However, the code I've written seems to think that all of the checkboxes correspond to the last entry widget. I need help iterating through the list and generating widgets that I can access in an outside function for every item in the list. Here is my code, using python 3.8.6 with IDLE:

import tkinter as tk
from tkinter import StringVar, IntVar

groups = ['A', 'B', 'C']

def update_var(item, e_dict, cb_val):   
    print(item)
    print(e_dict[item].get())
    print(cb_val[item].get())
    
    if cb_val[item].get() == 1:
        e_dict[item].set('CHECKBOX IS CLICKED')

def submit():
    pass

class App(tk.Tk):
    def __init__(self, *args, **kwargs):
        tk.Tk.__init__(self, *args, **kwargs)
        self.container = tk.Frame(self)

        self.container.pack(side='top', fill='both', expand=True)

        self.container.grid_rowconfigure(0, weight=1)
        self.container.grid_columnconfigure(0, weight=1)

        self.show_frame(MainWindow)

    def show_frame(self, cont):
        frame = cont(self.container, self)
        frame.grid(row=0, column=0, sticky='nsew')
        frame.tkraise()

class MainWindow(tk.Frame):
    def __init__(self, parent, controller, *args, **kwargs):
        global group_dict
        
        tk.Frame.__init__(self, parent, *args, **kwargs)
        
        container = tk.Frame()

        canvas = tk.Canvas(container)
        scrollbar = tk.Scrollbar(container, orient='vertical', command=canvas.yview)
        scrollable_frame = tk.Frame(canvas)

        scrollable_frame.bind(
            '<Configure>',
            lambda e: canvas.configure(
                scrollregion=canvas.bbox('all')
                )
            )

        canvas.create_window((0,0), window=scrollable_frame, anchor='nw')

        canvas.configure(yscrollcommand=scrollbar.set)

        label1 = tk.Label(scrollable_frame, text='SAMPLE PROGRAM')
        label1.config(font=('Arial', 20))
        label1.grid(row=0, column=0, columnspan=3, padx=2, pady=2)

        label2 = tk.Label(scrollable_frame, text='GROUP', width=13)
        label2.config(font=('Arial', 15))
        label2.grid(row=1, column=0, padx=2, pady=2)

        label3 = tk.Label(scrollable_frame, text='INPUT', width=13)
        label3.config(font=('Arial', 15))
        label3.grid(row=1, column=1, padx=2, pady=2)

        label4 = tk.Label(scrollable_frame, text='CHECKBOX', width=13)
        label4.config(font=('Arial', 15))
        label4.grid(row=1, column=2, padx=2, pady=2)

        e_dict = {}
        cb_val = {}
        num_lines = 0

        group_list = []
        
        for i, item in enumerate(groups):
            tk.Label(scrollable_frame, text=item, width=20).grid(row=i+2, column=0, padx=2, pady=2)
            
            e_dict[item] = StringVar()
            tk.Entry(scrollable_frame, textvariable=e_dict[item]).grid(row=i+2, column=1, padx=2, pady=2)

            #group_list.append(key)
            cb_val[item] = IntVar()
            tk.Checkbutton(scrollable_frame, variable = cb_val[item], command=lambda: update_var(item, e_dict, cb_val)).grid(row=i+2, column=2, padx=2, pady=2)

            num_lines += 2

        submit_btn = tk.Button(scrollable_frame, text='SUBMIT', width=20, command = lambda: submit())
        submit_btn.config(font=('Arial', 12))
        submit_btn.grid(row=num_lines+1, column=1, columnspan=2)

        container.place(x=0, y=0, width=490, height=640)
        scrollbar.pack(side="right", fill="y")
        canvas.pack(side='left', fill='both', expand=True)
        
if __name__ == '__main__':
    root = App()
    root.mainloop()