how to use nested for loop with on_parent in kivy

Question

i want to make nested for loop in kivy language by using on_perent then i try the slashes but there is error invalid indentation must be a multiple of 4 spaces i don't know what to do and there is no other than slashes

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

kv = Builder.load_string('''
#:import Button kivy.uix.button.Button
BoxLayout:
    BoxLayout:
        on_parent:for i in range(2):\n \t \b\b\b\b\b \
        on_parent:for i in range(3):\n \t \
        on_parent:self.add_widget(Button(text=str(i)))
''')

class TestApp(App):
    def build(self):
        return kv

TestApp().run()

Answer 1

This is a way of doing the nested for loop but I don't understand what you are trying to achieve

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

kv = Builder.load_string('''
#:import Button kivy.uix.button.Button
BoxLayout:
        BoxLayout:
                on_parent:
                        if not self.children: [self.add_widget(Button(text=str(j))) for i in range(2) for j in range(3)]
''')

class TestApp(App):
    def build(self):
        return kv

TestApp().run()