我无法在python中正确使用Gtk.get-text指令

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

def on_button_clicked(button):
    text = entry.get_text()
    print("输入的文本是：" + text)

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

entry = Gtk.Entry()
win.add(entry)

button = Gtk.Button(label="获取文本")
button.connect("clicked", on_button_clicked)
win.add(button)

win.show_all()
Gtk.main()