Example on how to show a very long text in label in a recycleview. With colored line numbers.

long_text.py

from kivy.app import App
from kivy.properties import ListProperty
from kivy.lang import Builder

long_text = 'This is an example to output a very long file as labels in a recycleboxlayout with line numbers and proper line breakings\n' * 1000 + " END"


KV = '''
<MyLabel@Label>:
    halign: "left"
    text_size: self.width, None
    height: self.texture_size[1]+8  # plus 8 to ad some spacing between the next line
    markup: True

RecycleView:
    viewclass: 'MyLabel'
    data: app.data
    RecycleBoxLayout:
        id: layout
        default_size: None, None
        default_size_hint: 1, None
        size_hint_y: None
        height: self.minimum_height
        orientation: 'vertical'
'''


class ScrollApp(App):
    data = ListProperty([{"text": "[color=3333ff]{}.[/color] {}".format(number,line)} for number,line in list(enumerate(long_text.split("\n")))])

    def build(self):
        return Builder.load_string(KV)


if __name__ == "__main__":
    ScrollApp().run()