python 窗口上新建两个按钮，两个标签，点击第一个按钮，改变第一个标签，点击第二个按钮，改变第二个标签

def firstchange():
    b1.configure(text = "Hello World")

def secondchange():
    b2.configure(background = "red")

import tkinter as tk
from tkinter import ttk

win = tk.Tk()
b1 = ttk.Label(win,text = "change1")
b1.grid(column = 0,row = 0)
b2 = ttk.Label(win,text = "change2",foreground = "green")
b2.grid(column = 1,row = 0)
bb1 = ttk.Button(win,text = "First",command = firstchange)
bb1.grid(column = 0,row = 1)
bb2 = ttk.Button(win,text = "Second",command = secondchange)
bb2.grid(column = 1,row = 1)

win.mainloop()