Kivy如何将函数的输出显示为文本

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.boxlayout import BoxLayout

class MyApp(BoxLayout):
    def __init__(self, **kwargs):
        super(MyApp, self).__init__(**kwargs)
        self.orientation = 'vertical'
        self.label = Label(text='输出结果将显示在这里')
        self.add_widget(self.label)

def my_function():
    # 执行需要输出的操作
    output = '这是函数的输出结果'
    # 更新文本标签的文本内容
    app.label.text = output

class MyApp(App):
    def build(self):
        return MyApp()

    def build(self):
        return MyApp()

if __name__ == '__main__':
    app = MyApp()
    app.run()