如何在不使用全局变量的情况下用函数内变量更新外部变量？

你当前代码的问题在于：调用AccountMenu(currentMenuState)时，只是执行了函数逻辑，但没有把函数返回的新状态赋值给currentMenuState。因为字符串是不可变类型，函数内部修改的menuState是局部变量，和外部的currentMenuState是完全独立的两个变量，所以外部状态一直没变化。

下面提供几种不用全局变量的解决方式：

方法1：接收函数返回值并赋值（最直接） #

这是最简洁的方案，直接把函数返回的新状态重新赋值给外部的currentMenuState：

currentMenuState = 'ACCOUNTSMENU'

def AccountMenu(menuState):
    print("1. View")
    print("2. Edit")
    print("3. Help")
    print("4. Quit")
    menuNav = int(input())
    if menuNav == 1:
        menuState = 'VIEWMENU'
    elif menuNav == 2:
        menuState = 'EDITMENU'
    elif menuNav == 3:
        print("Hint text")
    elif menuNav == 4:
        print("Closed the program and terminated all processes.")
        menuState = 'IDLE'
    else:
        print("Invalid input.")
    return menuState

while currentMenuState != 'IDLE':
    if currentMenuState == 'ACCOUNTSMENU':
        # 关键：把函数返回的新状态赋值给外部变量
        currentMenuState = AccountMenu(currentMenuState)
    elif currentMenuState == 'VIEWMENU':
        # 假设你有ViewMenu函数，同样用返回值更新状态
        currentMenuState = ViewMenu(currentMenuState)
    elif currentMenuState == 'EDITMENU':
        currentMenuState = EditMenu(currentMenuState)

方法2：用可变对象封装状态 #

如果不想每次都手动赋值，可以用字典这类可变对象来封装状态——函数内部修改可变对象的内容时，外部的对象会同步变化：

# 用字典封装当前菜单状态
menuState = {'current': 'ACCOUNTSMENU'}

def AccountMenu(state):
    print("1. View")
    print("2. Edit")
    print("3. Help")
    print("4. Quit")
    menuNav = int(input())
    if menuNav == 1:
        state['current'] = 'VIEWMENU'
    elif menuNav == 2:
        state['current'] = 'EDITMENU'
    elif menuNav == 3:
        print("Hint text")
    elif menuNav == 4:
        print("Closed the program and terminated all processes.")
        state['current'] = 'IDLE'
    else:
        print("Invalid input.")
    # 无需返回值，直接修改字典内容即可

while menuState['current'] != 'IDLE':
    if menuState['current'] == 'ACCOUNTSMENU':
        AccountMenu(menuState)
    # 其他菜单分支同理

方法3：用类管理菜单状态（适合复杂系统） #

如果菜单逻辑比较复杂，推荐用面向对象的方式，把状态和操作封装成类的属性和方法，结构更清晰，也更易维护：

class MenuSystem:
    def __init__(self):
        self.current_state = 'ACCOUNTSMENU'
    
    def account_menu(self):
        print("1. View")
        print("2. Edit")
        print("3. Help")
        print("4. Quit")
        menuNav = int(input())
        if menuNav == 1:
            self.current_state = 'VIEWMENU'
        elif menuNav == 2:
            self.current_state = 'EDITMENU'
        elif menuNav == 3:
            print("Hint text")
        elif menuNav == 4:
            print("Closed the program and terminated all processes.")
            self.current_state = 'IDLE'
        else:
            print("Invalid input.")
    
    def view_menu(self):
        # 实现VIEWMENU的逻辑
        print("\nView Menu:")
        print("1. Back to Account Menu")
        choice = int(input())
        if choice == 1:
            self.current_state = 'ACCOUNTSMENU'
    
    def run(self):
        while self.current_state != 'IDLE':
            if self.current_state == 'ACCOUNTSMENU':
                self.account_menu()
            elif self.current_state == 'VIEWMENU':
                self.view_menu()

# 启动菜单系统
menu_system = MenuSystem()
menu_system.run()

内容的提问来源于stack exchange，提问作者tesseract