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import tkinter as tk
win = tk.Tk()
win.title("我的窗口")
win.geometry("200x100")
labVar = tk.StringVar()
lab = tk.Label(win,textvariable = labVar,bg="blue",font=("Arial",12),width=15,height=2)
lab.pack()
on_hit = False
def btn_click():
    global on_hit
    if on_hit == False:
        on_hit = True
        labVar.set("Hello TK")
    else:
        on_hit = False
        labVar.set("")
btn = tk.Button(win,text = "显示",width=15,height=2,command=btn_click)
btn.pack()
win.mainloop()