如何让我的计算器用tkinter计算条目中的所有内容？

import tkinter as tk

window = tk.Tk()
window.title("计算器")

display = tk.Entry(window, width=30)
display.grid(row=0, column=0, columnspan=4)

# 创建数字按钮
buttons = []
for i in range(10):
    button = tk.Button(window, text=str(i), command=lambda i=i: on_button_click(str(i)))
    buttons.append(button)

# 创建运算符按钮
operators = ['+', '-', '*', '/']
for i, operator in enumerate(operators):
    button = tk.Button(window, text=operator, command=lambda operator=operator: on_button_click(operator))
    buttons.append(button)

# 创建等号按钮
equal_button = tk.Button(window, text='=', command=calculate)
buttons.append(equal_button)

# 将按钮放置在合适的位置
for i, button in enumerate(buttons):
    button.grid(row=(i+1)//4, column=i%4)

def on_button_click(text):
    display.insert(tk.END, text)

def calculate():
    expression = display.get()
    try:
        result = eval(expression)
        display.delete(0, tk.END)
        display.insert(tk.END, result)
    except:
        display.delete(0, tk.END)
        display.insert(tk.END, "Error")

window.mainloop()