KV, Kivy Language File (.kv)
The KV Developer file format
Files with the KV extension are used by Kivy, which is an open source Python library. Kivy is used to develop applications and programs that can be used across different platforms and are also multi-touch enabled. The KV file itself contains various kinds of data, such as definitions of rules and dynamic classes, templates, and a root widget.
Technical details of KV files
The root widget contained inside the KV file is a core building block in Kivy. Thus, many KV files are needed to build applications using this program. The rules specified in the KV file is used to modify a specific widget, while dynamic classes allow programmers to create new widgets. In former versions of KV files, templates were used as well, but they have been replaced by dynamic classes as of Kivy version 1.7.0 . In order for KV files to be correctly interpreted, they have to start with the Kivy header and the correct language version.