kivy/doc/sources/guide/quickstart.rst

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.. _quickstart:
Quickstart
==========
This page explains how to create a simple Kivy *"Hello world"* program.
This assumes you already have Kivy installed. If you do not, head over to the
:ref:`installation` section. We also assume basic `Python <http://docs.python.org/tutorial/>`_
2.x knowledge.
Create an application
---------------------
The base code for creating an application looks like this:
.. sourcecode:: python
from kivy.app import App
from kivy.uix.button import Button
class MyApp(App):
def build(self):
return Button(text='Hello World')
MyApp().run()
Save it as `myapp.py` and run it with your Python interpreter ::
$ python myapp.py
A window should open, showing a sole button (with the label 'Hello World') that
covers the entire window's area. That's all there is to it.
So what does that code do?
#. First, we import the :class:`~kivy.app.App` class, to be able to
subclass it.
By subclassing this class, your own class gains several features that
we already developed for you to make sure it will be recognized by
Kivy.
#. Next, we import the :class:`~kivy.uix.button.Button` class, to be able to
create an instance of a button with a custom label.
#. Then, we create our application class, based on the App class.
We extend the :meth:`~kivy.app.App.build` function to be able to return an
instance of :class:`~kivy.uix.button.Button`. This instance will be used
as the root of the widget tree (because we returned it).
#. Finally, we call :meth:`~kivy.app.App.run` on our application instance to
launch the Kivy process with our application inside.