[Tkinter] Inserting numbers into entry box in a widget

[Yoriz]

You cant call insert on a StringVar it does not have this method.
Entry widgets have an insert method maybe that what you are trying to do, you will need to keep a reference to the entry widget in the class to access it.
Also note that insert parameters of a Entry are an index and a string you have used an index and a int.

insert(index, string)
Inserts text at the given index. Use insert(INSERT, text) to insert text at the cursor, insert(END, text) to append text to the widget.

• index
  Where to insert the text.
  
• string
  The text to insert.
  

All the code you posted is overwhelming and not necessary to show the problem you are having, strip out the the unnecessary parts like below.

# imports

from tkinter import *

from tkinter import messagebox as ms


# main Class

class main:

    def __init__(self, master):
        # Window
        self.master = master
        # Some Usefull variables
        self.level1 = StringVar()  # lets
        self.monitor()

    def monitor(self):

        self.disp1 = Frame(self.master, padx=10, pady=10)

        Label(self.disp1, text='Level 1: ', font=(
            '', 20), pady=5, padx=5).grid(sticky=W)
        Entry(self.disp1, textvariable=self.level1,
              bd=5, font=('', 15)).grid(row=0, column=1)
        Button(self.disp1, text=' Display Counts ', bd=3, bg="green", font=(
            '', 15), padx=5, pady=5, command=self.level).grid()  # comand delet inm sqlite3
        self.disp1.pack()

    def level(self):

        lv = int(4)
        self.level1.insert(0, 4)
        print("Hello World")


root = Tk()

root.title("Bearing Current Program")

main(root)

root.mainloop()

When you get an error post the error traceback

Error:
Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Users\Dave\Anaconda3\lib\tkinter\__init__.py", line 1705, in __call__
    return self.func(*args)
  File "c:/Users/Dave/Documents/VS Code WorkSpaces/Python Forum/general/forumpost.py", line 34, in level
    self.level1.insert(0, 4)
AttributeError: 'StringVar' object has no attribute 'insert'

It is advisable not to use star imports
https://python-forum.io/Thread-Namespace...th-imports