python - 使用 .grid 时无法在 Tkinter 中调用单选按钮

Question

我正在尝试在 tkinter 中创建一组单选按钮，但在创建它们后无法调用它们。当我使用.pack()时，可以调用按钮，但是当使用.grid时，按钮无法调用。

def initialize():
    Label(window,text = "Customer Name").grid(column = 0, row = 0)
    customerName = StringVar()
    nameEntry = Entry(window,textvariable = customerName)
    nameEntry.grid(column = 1, row = 0)
    def firstPizza():
        Label(window,text = "Pizza 1").grid(column = 0,row = 1)
        pizzaCost = DoubleVar() #12 and 10
        largeButton = Radiobutton(window,text = "Large $15.95",value = 15.95,variable = pizzaCost)
        mediumButton = Radiobutton(window,text = "Medium $12.95",value = 12.95, variable = pizzaCost)
        smallButton = Radiobutton(window,text = "Small $10.95",value = 10.95, variable = pizzaCost)
        largeButton.grid(column = 0,row = 2)
        largeButton.invoke()
        mediumButton.grid(column = 1, row = 2)
        smallButton.grid(column = 2, row = 2)


    firstPizza()

这行largeButton.invoke()没有执行其预期目的，并且根本没有调用任何东西。

Answer 1

问题是 pizzaCost 是一个局部变量。调用有效，但随后变量被垃圾收集，并且值被丢弃。

如果将变量设置为全局变量，则对 invoke 的调用将起作用。鉴于您可能希望稍后能够访问该值，因此您几乎必须将其设为全局，因为您没有使用类。

在以下示例中，请注意 pizzaCost 如何在 firstPizza 内部定义为全局。

from tkinter import *
def initialize():
    Label(window,text = "Customer Name").grid(column = 0, row = 0)
    customerName = StringVar()
    nameEntry = Entry(window,textvariable = customerName)
    nameEntry.grid(column = 1, row = 0)
    def firstPizza():
        global pizzaCost
        Label(window,text = "Pizza 1").grid(column = 0,row = 1)
        pizzaCost = DoubleVar() #12 and 10
        largeButton = Radiobutton(window,text = "Large $15.95",value = 15.95,variable = pizzaCost)
        mediumButton = Radiobutton(window,text = "Medium $12.95",value = 12.95, variable = pizzaCost)
        smallButton = Radiobutton(window,text = "Small $10.95",value = 10.95, variable = pizzaCost)
        largeButton.grid(column = 0,row = 2)
        largeButton.invoke()
        mediumButton.grid(column = 1, row = 2)
        smallButton.grid(column = 2, row = 2)


    firstPizza()

window = Tk()
initialize()
window.mainloop()