函数内的全局变量

Question

我试图告诉一个函数使用place.forget（）从屏幕上删除按钮lb，但是由于出现了错误，因为我已将按钮lb定义为另一个函数中的全局变量，因此每次尝试调用它时它没有“看到”全局变量。 我知道为什么它会给我错误，但我不确定如何纠正它，任何帮助将不胜感激。

def page4():
    master.title('Page 4')
    #draw
    c19.grid(pady=slpady)
    c19.grid(row=sly,column=slx1)
    c20.grid(row=sly,column=slx2)
    c21.grid(row=sly,column=slx3)
    c22.grid(row=sly,column=slx4)
    c23.grid(row=sly,column=slx5)
    c24.grid(row=sly,column=slx6)
    rec.grid(row=rec_y, column=rec_x,columnspan=3)
    clear_4.grid(row=clear_y, column=clear_x,columnspan=3)
    #hide
    c1.grid_remove()
    c2.grid_remove()
    c3.grid_remove()
    c4.grid_remove()
    c5.grid_remove()
    c6.grid_remove()
    c7.grid_remove()
    c8.grid_remove()
    c9.grid_remove()
    c10.grid_remove()
    c11.grid_remove()
    c12.grid_remove()
    c13.grid_remove()
    c14.grid_remove()
    c15.grid_remove()
    c16.grid_remove()
    c17.grid_remove()
    c18.grid_remove()
    new_show.grid_remove()
    save_show.grid_remove()
    load_show.grid_remove()
    pre_1.grid_remove()
    pre_2.grid_remove()
    pre_3.grid_remove()
    pre_4.grid_remove()
    clear_1.grid_remove()
    clear_2.grid_remove()
    clear_3.grid_remove()
    lb.place_forget()

#Presets
def presets():
    master.title('Presets')
    pre_1.grid(row=1,column=1,padx=ppadx, pady=ppady)
    pre_2.grid(row=1,column=2,padx=ppadx, pady=ppady)
    pre_3.grid(row=2,column=1,padx=ppadx, pady=ppady)
    pre_4.grid(row=2,column=2,padx=ppadx, pady=ppady)
    global lb
    lb=Button(master,width=20,height=5,text='LOCK',bg='burlywood1',command=lockscreen)
    lb.place(x=450,y=580)

我得到的错误是：

Exception in Tkinter callback Traceback (most recent call last):
    File "C:\Python27\lib\lib-tk\Tkinter.py", line 1470, in __call__
        return self.func(*args)
    File "C:\Users\Josh Bailey\Desktop\pi_dmx\pi_dmx512py2.py", line 412, in page4
        lb.place_forget() NameError: global name 'lb' is not defined

Answer 1

在启动任何功能之前，请初始化lb。

Answer 2

我已经通过将全局lb和lb = Button（master，width = 20，height = 5，text ='LOCK'，bg ='burlywood1'，command = lockscreen）移到我的代码的顶部来解决了它没有任何功能，然后必须重新排列我的代码的其余部分，以使该按钮（锁屏）所调用的功能位于预设功能的上方。 谢谢您的帮助！