当Gtk.ComboBox中的活动项发生更改时更新Gtk.Label

import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk

def on_combo_changed(combo):
    active_text = combo.get_active_text()
    label.set_text(active_text)

window = Gtk.Window()
window.connect("destroy", Gtk.main_quit)

box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=6)
window.add(box)

combo = Gtk.ComboBoxText()
combo.append_text("Option 1")
combo.append_text("Option 2")
combo.append_text("Option 3")
combo.connect("changed", on_combo_changed)
box.pack_start(combo, False, False, 0)

label = Gtk.Label()
box.pack_start(label, False, False, 0)

window.show_all()
Gtk.main()