Python 使用按钮更改类变量

我正试图根据在internet上找到的教程（）构建一个简单的计算器。我试图重建他的代码，但只使用纯phython，而不是kv文件。这是我目前的代码：

from kivy.app import App
from kivy.uix.gridlayout import GridLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.uix.textinput import TextInput

class Window(GridLayout):
    def __init__(self,**kwargs):
        super(Window,self).__init__(**kwargs)
        self.rows=5
        self.padding=10
        self.spacing=10
        self.entry=TextInput(font_size=32)
        self.add_widget(self.entry)
        self.add_widget(Box1())


class Box1(BoxLayout):
    def __init__(self,**kwargs):
        super().__init__(orientation='horizontal',**kwargs)
        self.add_widget(CustButton(text='Hi'))


class CustButton(Button):
    def __init__(self,**kwargs):
        super(CustButton,self).__init__(font_size=32,**kwargs)
    def on_press(self):
        self.entry.text=self.text


class Calculator(App):
    def build(self):
        return Window()

if __name__=='__main__':
    Calculator().run()

问题是我一直收到这样的错误消息：“AttributeError:'CustButton'对象没有属性'entry'”

我已经尝试了很多事情，但都做不到！！那么，我如何通过按钮更改“Window.entry”的文本呢

---

非常感谢python新手

我在相关位置添加了评论

class Window(GridLayout):
    def __init__(self,**kwargs):
        super(Window,self).__init__(**kwargs)
        self.rows=5
        self.padding=10
        self.spacing=10
        self.entry=TextInput(font_size=32)
        self.add_widget(self.entry)
        self.box1 = Box1() # save box1 as an instance attribute
        self.add_widget(self.box1)
        # bind your on_press here ... where you can access the self.entry
        self.box1.button.bind(on_press=self.on_press)
    def on_press(self,target):
        self.entry.text=target.text


class Box1(BoxLayout):
    def __init__(self,**kwargs):
        super().__init__(orientation='horizontal',**kwargs)
        self.button = CustButton(text='Hi') # save an instance to our class
        self.add_widget(self.button)


class CustButton(Button):
    def __init__(self,**kwargs):
        super(CustButton,self).__init__(font_size=32,**kwargs)
    # def on_press(self):
    #    pass # self.entry.text=self.text

解决方案-App.get_running_App（）.root 使用

App.get_running_App（）.root

获取根的实例并访问类属性、方法和WDIGET

片段 输出

---

再问一个问题。无法访问“Window.entry.text=x”中其他类的属性是否正常？您是否总是必须在类本身内部才能更改其属性？

class CustButton(Button):
    def __init__(self, **kwargs):
        super(CustButton, self).__init__(font_size=32, **kwargs)

    def on_press(self):
        App.get_running_app().root.entry.text = self.text