from tkinter import *
root = Tk()
root.geometry("500x500")
def reset():
#win.destroy()
pass
def modal():
win = Toplevel(root)
butReset = Button(win, text = 'close modal win', command = reset())
butReset.pack()
button = Button(root, text = 'open modal', command = modal)
button.pack()
root.mainloop()