Write once, run anywhere

This whole situation creates a demand for a universal, multi-platform way to program. The problem isn't exactly new: one solution to it, created by Sun in 1995, is the Java programming language. Its marketing promise—write once, run anywhere—was never fulfilled and the language itself is unreasonably cumbersome to use. This led to many mocking variations of the slogan, culminating with write once, run away that refers to many developers abandoning Java in favor of better programming languages, including Python.

Not coincidentally, Kivy—the main topic of this book—is a graphical user interface library facilitating easy creation of multi-platform Python applications. The main features of Kivy toolkit are as follows:

Speaking of third-party packages, Kivy can be seen as a superset of many battle-tested components: a large part of its functionality relies on well-known libraries such as Pygame, SDL, and GStreamer. The API that Kivy exposes, however, is very high-level and unified.

It's worth mentioning that Kivy is free and open source MIT licensed software. In practice, this means that you can use it commercially without paying licensing fees. Its full source code is hosted on GitHub, so you can also patch bugs or add new features to it.