Python kivy get labels from *.py file in kivy file

Question

I am trying to get labels from a python file (labels.py) and inject these labels into a label inside of a kivy file (pong.kv).

# main.py
from kivy.app import App
from kivy.uix.widget import Widget


class PongGame(Widget):
    pass


class PongApp(App):
    def build(self):
        return PongGame()


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

This is the labels.py file:

# labels.py
WORLD = "World"

And this is the kv file:

#: kivy 1.10.1
#: import labels pygame.labels

<PongGame>:
    canvas:
        Rectangle:
            pos: self.center_x - 5, 0
            size: 10, self.height

    Label:
        font_size: 70
        center_x: root.width / 4
        top: root.top - 50
        text: WORLD

If I run the main.py file I get an error "NameError: name 'WORLD' is not defined". Replacing WORLD by "World" runs without any problems.

Answer 1

Assuming you do not have the pygame library installed (if you have the pygame library installed you will have a conflict in the import), the import into .kv complies with the same python rules according the docs, so your import into .kv:

#: import labels pygame.labels

it would translate into python in the following way:

from pygame.labels as labels

So, keeping in mind the above, the way to obtain "WORLD" is using the namespace, that is, labels.WORLD. Consequently the .kv should be the following:

#: kivy 1.10.1
#: import labels pygame.labels

<PongGame>:
    canvas:
        Rectangle:
            pos: self.center_x - 5, 0
            size: 10, self.height

    Label:
        font_size: 70
        center_x: root.width / 4
        top: root.top - 50
        text: labels.WORLD