Tkinter Toplevel窗口与主窗口通信：动态更新标签内容

from tkinter import *

root = Tk()
root.title('change text')
Label1 = Label(root, text = 'Change me')
Label1.pack()

def presto():
     # 尝试访问 entry1，但 entry1 在 open_sub 函数内部定义
     Label1.configure(text = entry1.get()) 

def open_sub():
     top1 = Toplevel(root)
     top1.title('Buttons')
     label1 = Label(top1, text = 'Type Something')
     entry1 = Entry(top1, width = 20) # entry1 在这里定义
     button1 = Button(top1, text = "execute", command = presto)
     button2 = Button(top1, text = 'close', command = top1.destroy)
     label1.pack()
     entry1.pack()
     button1.pack()
     button2.pack()

button1 = Button(root, text = 'page 2', command = open_sub)
button1.pack()

root.mainloop()

from tkinter import *

# 1. 主窗口和Label的定义保持不变
root = Tk()
root.title('Tkinter Toplevel Communication')
main_label = Label(root, text='Initial Text in Main Window')
main_label.pack(pady=10)

# 2. 修改 presto 函数，使其接受一个参数
def update_main_label(text_to_display):
    """
    更新主窗口的Label文本。
    :param text_to_display: 要显示的新文本。
    """
    main_label.configure(text=text_to_display)

def open_sub_window():
    """
    打开一个Toplevel子窗口，用于获取用户输入。
    """
    top_window = Toplevel(root)
    top_window.title('Input for Main Window')
    top_window.transient(root) # 设置为模态窗口，使其在主窗口之上

    # 子窗口内的组件
    sub_label = Label(top_window, text='Enter text to update main window:')
    sub_label.pack(pady=5)

    sub_entry = Entry(top_window, width=40)
    sub_entry.pack(pady=5)
    sub_entry.focus_set() # 设置焦点，方便用户直接输入

    # 3. 关键修改：使用 lambda 表达式传递参数
    # 当 button_execute 被点击时，lambda 函数会执行 sub_entry.get()
    # 并将其结果作为参数传递给 update_main_label 函数。
    button_execute = Button(top_window, text="Update Main Label", 
                            command=lambda: update_main_label(sub_entry.get()))
    button_execute.pack(pady=5)

    button_close = Button(top_window, text='Close', command=top_window.destroy)
    button_close.pack(pady=5)

    # 绑定回车键到更新操作
    top_window.bind('<Return>', lambda event: update_main_label(sub_entry.get()))

# 主窗口的按钮，用于打开子窗口
open_button = Button(root, text='Open Input Window', command=open_sub_window)
open_button.pack(pady=10)

root.mainloop()