返回没有全局变量的变量？ Tkinter

Question

我想把这个封闭在 function 中。 如果我将颜色设为全局变量，它会起作用，但否则不起作用。 有没有办法在没有全局变量的情况下完成这项工作？

import tkinter

def pick_color():
    root = tkinter.Tk()
    color = "blue"
    def blue():
        color = "blue"
        root.destroy()
    def red():
        color = "red"
        root.destroy()
    b = tkinter.Button(root, text="blue", command = blue)
    b.pack()
    c = tkinter.Button(root, text="red", command= red)
    c.pack()
    root.mainloop()
    return color

print(pick_color())

Answer 1

我想把这个封闭在 function

That's not how python works, variables are local to the function they are defined in, if you want to make a variable assessable to multiple function you got 2 options, either make it global, or use a class.

import tkinter

class color():
    def __init__(self):
        self.color = "blue"
        self.root = tkinter.Tk()
        
    def blue(self):
        self.color = "blue"
        self.root.destroy()
        
    def red(self):
        self.color = "red"
        self.root.destroy()

    def pick_color(self):
        b = tkinter.Button(self.root, text="blue", command = self.blue)
        b.pack()
        c = tkinter.Button(self.root, text="red", command = self.red)
        c.pack()
        self.root.mainloop()
        return self.color

choose = color()
print(choose.pick_color())

在这里，我定义了 class 颜色并将变量self.color设置为 class 的本地变量，因此可以通过任何类方法访问它，例如blue()和red() 。

Answer 2

使用您现在拥有的东西， red和blue正在创建自己的新变量，称为color ； 他们没有重新分配pick_color的color 。 您需要告诉nonlocal内部color变量是 nonlocal ：

def pick_color():
    root = tkinter.Tk()
    color = "blue"
    def blue():
        nonlocal color  # color is "nonlocal" to blue
        color = "blue"
        root.destroy()
    def red():
        nonlocal color  # And similarly, color is also nonlocal to red
        color = "red"
        root.destroy()
    b = tkinter.Button(root, text="blue", command = blue)
    b.pack()
    c = tkinter.Button(root, text="red", command= red)
    c.pack()
    root.mainloop()
    return color

如果没有 nonlocal ， nonlocal不知道您要引用现有的外部颜色，因为 Python 没有变量声明。