python button改变按钮上的文本

import tkinter as ti
Break = 0
def Click():
   global Break
   if Break == 0:
      Bu.place_forget()  
      Bu2.place(x=30,y=30)   #显示按钮2
      Break = 1
   else:        
     Bu2.place_forget()      #显示按钮1
     Bu.place(x=30,y=30)
     Break = 0

Wi = ti.Tk()                 #设置窗口
Wi.geometry("400x200")
Wi.title("机器人终端")

Bu = ti.Button(Wi,fg = "white",bg = "#87CEEB",text = "暂停",width=5,height=1,command=Click)
Bu.place(x = 30,y = 30)      #设置按钮1

Bu2 = ti.Button(Wi,fg = "white",bg = "#87CEEB",text = "开始",width=5,height=1,command=Click)
Bu2.place(x = 30,y = 30)     #设置按钮2并隐藏
Bu2.place_forget()


Wi.mainloop()