我正在制作一个python kivy程序，其中我有不同的屏幕，并且根据不同的屏幕，它们各自的Screen类中的功能也不同，但是现在我想将另一个屏幕类的功能访问到其他类。 这是我的代码：

class CustomSlips(Screen):
def __init__(self,**kwargs):
    super(CustomSlips,self).__init__(**kwargs)
slips = []
def input_append(self,list):
    for i in range(0,4):
        for j in range(0,3):
            list.append(list[i])
class DefaultSlips(Screen):
Custom = CustomSlips()
def Flowerscopy(self):
    Flowers = ["Rose","Sunflower","Tulips","Marigold"]
    Custom.slips = copy.copy(Flowers)
    print(Custom.slips)

和kivy文件是：

<CustomSlips>:
    name: "CustomSlips"
    BoxLayout:
        Button:
            pos_hint: {"center_x":0.5,"top":0.4}
            size_hint: 0.5,1.1
            text:"Write On Slips"
            on_release:
                app.root.transition = SlideTransition(direction = 'left')
                app.root.current = "PlayScreen"
                root.slips.append(slip1.text)
                root.slips.append(slip2.text)
                root.slips.append(slip3.text)
                root.slips.append(slip4.text)
                root.input_append(root.slips)
                print(root.slips)
<DefaultSlips>:
    name: "DefaultSlips"
    BoxLayout:
        orientation: "vertical"
        size_hint: 0.75,0.50
        pos_hint:{"center_x":0.5,"top":0.75}
        Button:
            text: "Flowers"
            size_hint: 0.4,2.5
            pos_hint:{"center_x":0.5}
            on_release:
                app.root.transition = SlideTransition(direction = 'left')
                app.root.current = "PlayScreen"
                app.root.Flowerscopy()

当我使用函数Flowerscopy（）并尝试更改CustomSlips屏幕的清单列表时，在DefaulSlips屏幕上出现错误。 帮帮我

谢谢