kivyで簡単なプログラムを試しに作っていたんですが
題にあるよう、インスタンス?をまたいでの変数代入を行うとエラーがおきます

TypeError: 'kivy.properties.DictProperty' object has no attribute '__getitem__'

class pullscreen(Screen):
    def clicked(self):
        x = np.random.randint(1,10,1)
        if x == 5:
            result.ids["res"].text = "1"
        elif x % 2 == 0:
            result.ids["res"].text = "2"
        else:
            result.ids["res"].text = "3"
        sm.current = "ans"

class result(Screen):
    def back(self):
        sm.current = "pull"

self.idsとするとそのインスタンス内の変数を指定するため望む結果が得られません。
どうすれば良いのでしょうか？よろしくお願いします

pyファイル

from kivy.config import Config
Config.set("graphics", "resizable", False)
Config.set("graphics", "width", 640)
Config.set("graphics", "height", 480)

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen

import numpy as np

sm = ScreenManager()

class pullscreen(Screen):
    def clicked(self):
        x = np.random.randint(1,10,1)
        if x == 5:
            result.ids["res"].text = "1"
        elif x % 2 == 0:
            result.ids["res"].text = "2"
        else:
            result.ids["res"].text = "3"
        sm.current = "ans"

class result(Screen):
    def back(self):
        sm.current = "pull"


class Amidakuji(App):
    def build(self):
        sm.add_widget(pullscreen(name = "pull"))
        sm.add_widget(result(name = "ans"))
        return sm


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

kvファイル

<PaddingBoxLayout@BoxLayout>:
    padding: 20

<pullscreen>:
    BoxLayout:
        orientation: "vertical"
        canvas.before:
            Color:
                rgba: 0.9,0.9,0.9,1
            Rectangle:
                pos: self.pos
                size: self.size
        Label:
            text: "Amidakuji"
            color: 0,0,0,1
            size_hint_y: 0.2
            font_size: 32

        BoxLayout:
            orientation: "horizontal"
            Button:
                text: "uranau"
                on_press: root.clicked()

<result>:
    BoxLayout:
        orientation: "vertical"
        canvas.before:
            Color:
                rgba: 0.9,0.9,0.9,1
            Rectangle:
                pos: self.pos
                size: self.size
        Label:
            text: "result"
            color: 0,0,0,1
            size_hint_y: 0.2
            font_size: 32

        BoxLayout:
            orientation: "horizontal"

            Label:
                id: res

            Button:
                text: "mo-ikkai, uranau"
                on_press: root.back()