KIVY: How to change label colour?

Question

My for loop creates a simple list of labels within a scrollview, instead of changing the font size and colour in the python file, I would rather customise the labels within my KV file. Is this possible?

I know I can use ids to reference a label in the KV file, but I cant wrap my head around how to do it here.

If I create a label in my python file, is it good practice to customise in my kv file or continue to customise it in the python file. What is the best way to go about this?

*.py

import kivy
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.properties import ObjectProperty
from kivy.properties import StringProperty
from kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout
from kivy.uix.scrollview import ScrollView
from kivy.lang import Builder
from kivymd.app import MDApp
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.clock import Clock
from kivy.uix.button import Button
from kivy.core.window import Window

class FirstWindow(Screen):
    def __init__(self, **kwargs):
        super(FirstWindow, self).__init__(**kwargs)
        Clock.schedule_once(self.create_scrollview)

    def create_scrollview(self, dt):
        list1 = ['1','2','3','4','5','6','7','8','9','10','11','12']
        layout = GridLayout(cols=1, spacing=10, size_hint_y=None)
        layout.bind(minimum_height=layout.setter("height"))

        for x in list1:
            l = Label(text=x, size=(10, 50), size_hint=(1, None)) <----- Change the font colour in my kv file
            layout.add_widget(l)

        scrollview = ScrollView(size_hint=(1, None), size=(Window.width, Window.height))
        self.view.add_widget(scrollview)
        scrollview.add_widget(layout)
        

class WindowManager(ScreenManager):
    pass

kv = Builder.load_file('NearMe.kv')

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

*.kv

WindowManager:
    FirstWindow:

<FirstWindow>:
    view: view
    BoxLayout:
        orientation: 'vertical'

        BoxLayout:
            size: (64, 64)
            size_hint: (1, None)

            Label:
                text: "NearMeApplications"
                canvas.before:
                    Color:
                        rgba: .5, .5, .5, 1
                    Line:
                        width: 2
                        rectangle: self.x, self.y, self.width, self.height

        ScrollView:
            id: view
            canvas.before:
                Color:
                    rgba: .8, .8, .8, 1
                Line:
                    width: 2
                    rectangle: self.x, self.y, self.width, self.height
                  

Answer 1

if i understand your question well the best way to use kivy.properties this is a part of project a function which check the user name and passwords before saving it and change the text and color of message in each case

.py

from kivy.properties import StringProperty, ColorProperty

class SettingsWindow(Screen):
    warning_message = StringProperty()
    warning_color = ColorProperty()

    def save_user(self, uname, pw1, pw2):
        if len(uname) > 3:
            if len(pw1) > 3:
                if pw1 == pw2:
                    self.warning_color = 0.5, 1, 0.5, 1
                    self.warning_message = "data saved"
                else:
                    self.warning_color = 1, 0.5, 0.5, 1
                    self.warning_message = "not the same password"
            else:
                self.warning_color = 1, 0.4, 0.4, 1
                self.warning_message = "password must be more than 3 chrs"
        else:
            self.warning_color = 1, 0.3, 0.3, 1
            self.warning_message = "User Name must be more than 3 chrs"

    pass

.kv

<SettingsWindow>:
    name:'setting'
    GridLayout:
        cols:1
        Label:
            text:'change user data'
            font_size:18
            size_hint:(0.1,0.1)

        GridLayout:
            padding:[10,10]
            size_hint:(1,0.2)
            cols:2
            rows:3
            Label:
                text:'User Name'
                font_size:18
            BoxLayout:
                padding:[10,10]
                TextInput:
                    id:uname
                    font_size:18
            Label:
                text:'password'
                font_size:18
            BoxLayout:
                padding:[10,10]
                TextInput:
                    id:pw1
            Label:
                text:'repeat password'
                font_size:18
            BoxLayout:
                padding:[10,10]
                TextInput:
                    id:pw2
                    
        Label:
            id:warning_message
            font_size:18
            size_hint:(1,.1)
            color: root.warning_color  #-------------look at this
            text : root.warning_message  #-------------look at this
        GridLayout:
            padding:[15,15]
            size_hint:(0.1,.1)
            cols:2
            Button:
                text:'Save User Data'
                on_release:
                    root.save_user(uname.text,pw1.text,pw2.text)
            Button:
                text:'cancel'
                

Answer 2

class MyTestApp(App):
        def build(self):
            return Button(text="HELLO", color=(0, 0, 5, 1), background_color=(7, 4, 5, 1), font_size=150)


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

Answer 3

You can define your own customized Label like this:

def MyLabel(Label):
    pass

Then in your kv make a rule for MyLabel:

<MyLabel>:
    color: 1,0,0,1
    size: 10, 50
    size_hint: 1, None

And in your loop:

    for x in list1:
        l = MyLabel(text=x) <----- Change the font colour in my kv file
        layout.add_widget(l)

Answer 4

You just need to add color: r,g,b,a.

Label:
    text: "NearMeApplications"
    color: 1,0,1,1

Answer 5

Correct me if I'm wrong, but it is not possible to set the value of any widget that is initiallized in the python file from the .kv file, as it is only added AFTER the entire .kv file is loaded, which would most likely result in an error. Though you can still edit the color in the python file, which would require ids to be added into individual label, something like this:

for x in list1:
    l = Label(id=x, text=x, size=(10, 50), size_hint=(1, None)) #ids from the list1 list
    layout.add_widget(l)