combo_box.py

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.uix.dropdown import DropDown
from kivy.lang import Builder

Builder.load_string("""
<ComboBox>
    cols: 1

    DropDown:
        Button:
            text: 'My first Item'
        Label:
            text: 'Unselectable item'
        Button:
            text: 'My second Item'
""")


class ComboBox(BoxLayout):

    def __init__(self):
        BoxLayout.__init__(self)


if __name__ == "__main__":
    class TestApp(App):
    
        def build(self):
            widget = ComboBox()
            return widget

    TestApp().run()