如何在使用函数时不借助全局变量实现tkinter widgets的移除

你遇到的警告是因为全局变量仅在函数内部赋值，模块顶层没有预先定义，下面两种方案可完全规避全局变量，同时方便后续扩展界面切换逻辑：

方案1：面向对象封装（最推荐，可维护性最高） #

把所有界面逻辑封装为自定义类，组件和状态都作为实例属性存储，是Tkinter开发的标准实践，后续加第二组组件、返回逻辑的扩展成本极低：

from tkinter import *

class App:
    def __init__(self, root):
        self.win = root
        self.win.geometry("1270x725+0+0")
        # 可分别存储多组界面的组件
        self.first_page_widgets = {}
        self.second_page_widgets = {}
        
        # 初始化页面
        self.init_first_page()
        self.init_switch_button()
    
    def something_happens(self, e1, e2, e3):
        print('something is supposed to happen when an option is pressed but that\'s not important')
    
    def init_first_page(self):
        category_names = ['all', 'electrical', 'mechanical', 'optics']
        self.first_page_widgets['category_variable'] = StringVar(self.win)
        self.first_page_widgets['category_variable'].set(category_names[0])
        self.first_page_widgets['category_menu'] = OptionMenu(
            self.win, 
            self.first_page_widgets['category_variable'], 
            *category_names
        )
        self.first_page_widgets['category_menu'].config(
            width=10, font=('Arial', 20), highlightthickness=0
        )
        self.first_page_widgets['category_menu'].place(relx=.45, rely=.3)
        self.first_page_widgets['category_variable'].trace('w', self.something_happens)
    
    def switch_to_second_page(self):
        # 隐藏第一页所有组件
        for widget in self.first_page_widgets.values():
            if isinstance(widget, Widget):
                widget.place(relx=2)
        # 这里可以加第二页组件的初始化/显示逻辑
        # if not self.second_page_widgets:
        #     self.init_second_page()
        # for widget in self.second_page_widgets.values():
        #     if isinstance(widget, Widget):
        #         widget.place(xxx)
    
    def init_switch_button(self):
        button = Button(
            self.win, 
            text='this is suppose to get rid of the option menu widget', 
            font=('Arial', 20),
            command=self.switch_to_second_page
        )
        button.place(relx=.2, rely=.5)

if __name__ == "__main__":
    win = Tk()
    app = App(win)
    win.mainloop()

方案2：轻量改造（小项目低改动选择） #

如果不想重构为类结构，可以通过函数返回值存储组件，用lambda给回调传参，改动量极小：

from tkinter import *

win = Tk()
win.geometry("1270x725+0+0")

def something_happens(e1, e2, e3):
    print('something is supposed to happen when an option is pressed but that\'s not important')

def category_option_menu():
    category_names = ['all', 'electrical', 'mechanical', 'optics']
    category_variable = StringVar(win)
    category_variable.set(category_names[0])
    category_drop_down_menu = OptionMenu(win, category_variable, *category_names)
    category_drop_down_menu.config(width=10, font=('Arial', 20), highlightthickness=0)
    category_drop_down_menu.place(relx=.45, rely=.3)
    category_variable.trace('w', something_happens)
    # 返回创建的组件给外部存储
    return category_drop_down_menu, category_variable

def hide_widget(widget):
    widget.place(relx=2)

# 组件存在局部变量中，无需全局变量
category_menu, category_var = category_option_menu()

button = Button(
    win, 
    text='this is suppose to get rid of the option menu widget', 
    font=('Arial', 20),
    command=lambda: hide_widget(category_menu)
)
button.place(relx=.2, rely=.5)

win.mainloop()

补充说明 #

你当前用place(relx=2)隐藏组件的方案很适合频繁切换的场景，要恢复第一页组件时，只需要重新调用对应组件的place()方法设置回原坐标即可，不需要销毁重建，性能更好。

内容的提问来源于stack exchange，提问作者neo_codex