Create Your First Kivy App in Python | 3 Ways to Build UI (KV File Explained)

The goal of this series is to teach you how to create mobile applications using Kivy. I'm using the Kivy library, but feel free to use any Python UI framework you're comfortable with. 

Part 1: Basic Structure of a Kivy App 

Let’s begin with the basic structure of a Kivy app — something you'll use in almost every project. Here’s what that structure looks like:

from kivy.app import App

class MyKivy(App):

    def build(self):

        pass

if __name__ == "__main__":

    MyKivy().run()

• We first import App from kivy.app. This is the core class that controls your entire app — like a movie director!
• Next, we create our own class MyKivy, which inherits from App.
• Inside that, we define the build() method — this is kind of like an initializer or onStart() method in other frameworks. It runs when the app starts.
• Lastly, the if __name__ == "__main__" block tells Python to run the app when this file is executed.

Part 2: Displaying a Label (Using Python Only)

Let’s add a simple label so something shows up on the screen.

We’ll import Label from kivy.uix.label, and return it in our build() function:

from kivy.uix.label import Label

class MyKivy(App):

    def build(self):

        return Label(text="Hello from Kivy!")

Part 3: Cleaner Method — KV Language Inside Python

Now let’s talk about a cleaner and more professional way to write your UI using KV Language — Kivy’s own markup-style language.

It’s similar to HTML in concept — it separates your design (UI) from your logic (Python code).

Here’s how to do it using a KV string inside your Python code:

from kivy.app import App

from kivy.lang import Builder

KV = '''

Label:

    text: "Hello from KV!"

'''

class MyKivy(App):

    def build(self):

        return Builder.load_string(KV)

We’ve imported Builder from kivy.lang, created a simple KV string with a label, and returned it using Builder.load_string().

Run the app, and you’ll see the same result — but the code is more organized and easier to read.

Part 4: Most Professional — Using a Separate .kv File

Now let’s take it one step further — using a completely separate .kv file, just like using a separate HTML file in web development.

1. Create a new file named mydesign.kv

2. Inside that file, just write:

Label:

    text: "Hello from KV separate file!"

Update your Python code like this:

from kivy.app import App

class MyDesign(App):

    pass

if __name__ == "__main__":

    MyDesign().run()

Here’s the magic: Kivy will automatically load the .kv file if its name matches the class name in lowercase (MyDesign → mydesign.kv).

Run it — and voilà! Same output, but with much cleaner structure.

If you enjoyed this video, please like, subscribe, and hit the bell icon so you don’t miss the next lesson.
And if anything was unclear, drop a comment — I’m always here to help.

Thanks for watching — I’ll see you in the next tutorial.
Until then, peace and happy coding!

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