# Tk_entry_limit.py

# Tk_entry_limit.py

import tkinter

root = tkinter.Tk()
myvar = tkinter.StringVar()
myvar.set('')
mywidget = tkinter.Entry(root,textvariable=myvar,width=30)
mywidget.pack()

top2rows = '1234567890qwertyuiopQWERTYUIOP()\|_+-='
def instant_relay(*t):
    inStr = myvar.get()
    if inStr:
        if (inStr[-1] not in top2rows) or len(inStr) > 6:
            print(f"Key Entry Rejected... [{inStr[-1:]}]")
            inStr = inStr[:-1]
    myvar.set(inStr)
    mywidget.update_idletasks()

myvar.trace('w',instant_relay)

root.mainloop()