Tkinter通过组合框选项调用对应函数并在文本框输出的问题

出于学习目的，需要实现组合框（combobox）选项选中后调用对应函数的功能：

• 选中Item 1时，调用function_item1()，文本框（textbox）显示This is function: function_item1
• 选中Item 2、Item 3时同理触发对应函数、展示匹配文本
• 要求尽量保留原有代码逻辑结构，不做过多改动

当前运行代码后，文本框输出为This is function: None，不符合预期。

from tkinter import ttk
import tkinter as tk
from tkinter import *

root = tk.Tk()
root.geometry("400x150")

combobox=ttk.Combobox(root, width = 18)
combobox.place(x=15, y=15)
combobox['value'] = ["Item 1", "Item 2", "Item 3"]
combobox.set("Select")

textbox = tk.Text(root,width=43,height=2)
textbox.place(x=15, y=50)


def all_function():

    a = b = c = None

    #function 1
    if combobox.get() == "Item 1":
        def function_item1():
            a = "function_item1"


    #function 2      
    if combobox.get() == "Item 2":
        def function_item2():
            b = "function_item2"

            
    #function 3
    if combobox.get() == "Item 3":
        def function_item3():
            c = "function_item3"

            
    #PRINT FUNCTIONS
    def print():
        text = f"This is function: {a or b or c}"
        textbox.insert(tk.END, text)

    print()

button2 = Button(root, text="Print", command = all_function)
button2.pack()
button2.place(x=15, y=100)

• 各if分支内仅定义了function_item1/2/3，没有实际调用，函数内的赋值逻辑从未执行
• 子函数内直接给a/b/c赋值会被识别为子函数的局部变量，不会修改all_function外层作用域的a/b/c初始值，因此三个变量始终为None
• 自定义函数命名为print会覆盖Python内置的print()方法，存在隐性bug
• 遗漏窗口事件循环启动语句root.mainloop()，运行时可能出现窗口无响应问题

from tkinter import ttk
import tkinter as tk
from tkinter import *

root = tk.Tk()
root.geometry("400x150")

combobox=ttk.Combobox(root, width = 18)
combobox.place(x=15, y=15)
combobox['value'] = ["Item 1", "Item 2", "Item 3"]
combobox.set("Select")

textbox = tk.Text(root,width=43,height=2)
textbox.place(x=15, y=50)


def all_function():

    a = b = c = None

    #function 1
    if combobox.get() == "Item 1":
        def function_item1():
            nonlocal a
            a = "function_item1"
        function_item1()


    #function 2      
    if combobox.get() == "Item 2":
        def function_item2():
            nonlocal b
            b = "function_item2"
        function_item2()

            
    #function 3
    if combobox.get() == "Item 3":
        def function_item3():
            nonlocal c
            c = "function_item3"
        function_item3()

            
    #PRINT FUNCTIONS
    def show_result():
        textbox.delete(1.0, tk.END)
        text = f"This is function: {a or b or c}"
        textbox.insert(tk.END, text)

    show_result()

button2 = Button(root, text="Print", command = all_function)
button2.pack()
button2.place(x=15, y=100)

root.mainloop()

• 每个分支内定义完对应function_itemX后新增调用语句，保证选中对应项时函数实际执行
• 子函数内通过nonlocal关键字声明a/b/c为外层作用域变量，解决赋值不生效的问题
• 将原自定义print函数重命名为show_result，避免覆盖内置方法
• 新增文本框清空逻辑，避免多次点击按钮时内容重复追加
• 补充root.mainloop()启动窗口事件循环，保证交互正常

内容的提问来源于stack exchange，提问作者user18313765