start.py

import tkinter as tk
from src.main import Main

def hello():
    print("Hello World!")

class MainApplication(tk.Frame):
    def __init__(self, parent, *args, **kwargs):
        tk.Frame.__init__(self, parent, *args, **kwargs)
        self.parent = parent
        self.main = Main(self, bg="#c6c6c6")

        self.main.pack(side="top", fill="both", expand=True)


if __name__ == "__main__":
    root = tk.Tk()
    root.minsize(600, 400)
    root.title("Translation GUI")

    menubar = tk.Menu(root)

    # create a pulldown menu, and add it to the menu bar
    filemenu = tk.Menu(menubar, tearoff=0)
    filemenu.add_command(label="Open", command=hello)
    filemenu.add_command(label="Save", command=hello)
    filemenu.add_separator()
    filemenu.add_command(label="Exit", command=root.quit)
    menubar.add_cascade(label="File", menu=filemenu)

    # create more pulldown menus
    editmenu = tk.Menu(menubar, tearoff=0)
    editmenu.add_command(label="Cut", command=hello)
    editmenu.add_command(label="Copy", command=hello)
    editmenu.add_command(label="Paste", command=hello)
    menubar.add_cascade(label="Edit", menu=editmenu)

    helpmenu = tk.Menu(menubar, tearoff=0)
    helpmenu.add_command(label="About", command=hello)
    menubar.add_cascade(label="Help", menu=helpmenu)

    # display the menu
    root.config(menu=menubar)

    MainApplication(root, bg="blue").pack(side="top", fill="both", expand=True)
    root.mainloop()