为什么代码为我的两个变量提出了NameError？

Question

单击NEXT按钮后，将为l3.destroy()和产生一个NameError NEXT.destroy。我想不出它为什么这么说l3并且NEXT没有定义的原因。有人可以看看我的代码并向我解释吗？#Import tkinter module and random from tkinter modulefrom tkinter import *import randomimport timewin = Tk()win.configure(cursor='gumby', bg='yellow')win.title('A sImPlE gUeSsInG gAmE')win.wm_iconbitmap('favicon.ico')number = random.randint(1, 101) #set number as a random integerf = Frame(win)#No play button(NO)def clicked():    win.destroy()#Play button (YES)def clicked1():    #Erase previous screen    l.destroy()    l2.destroy()    NO.destroy()    YES.destroy()    win.title('Are you READY?')    win.wm_iconbitmap('favicon.ico')    win.configure(background = "deep sky blue", cursor='rtl_logo')    f2 = Frame(win)    l3 = Label(win, text = 'The rule is simple. You have 5 chances to \n guess what number I am thinking of.', bg = 'deep sky blue', fg = 'yellow', font=('Snap ITC', 20))    l3.grid(row = 1, column = 4, columnspan=5)    #'Next' button    NEXT = Button(win, text = 'NEXT', command=clicked2)    NEXT.grid(row = 5, column = 5)#NEXT button commanddef clicked2():    win.title('Are you READY?')    win.wm_iconbitmap('favicon.ico')    win.configure(background = "deep sky blue", cursor='rtl_logo')    f3 = Frame(win)    l3.destroy() #NameError: name 'l3' is not defined <------------------    NEXT.destroy()#NameError: name 'NEXT' is not defined <------------------    l4 = Label(win, text = 'I am thinking of a number between 1 to 100.\n Good Luck!', bg = 'deep sky blue', fg = 'yellow', font=('Snap ITC', 20))    l4.grid(row = 1, column = 3, columnspan=5)    BEGIN = Button(win, text ='BEGIN')    BEGIN.grid(row = 4, column = 4)

Answer 1

使用全局变量的函数需要将每个变量显式声明为全局变量。例如：

n = 2

def foo():

    n += 1

foo()

print(n) # Prints: 2

添加global n将解决问题

n = 2

def foo():

    global n

    n += 1

foo()

print(n) # Prints: 3