The WPI Robotics Library (WPILib) is the standard software library provided for teams to write code for their FIRST® Robotics Competition (FRC®) robots. A software library is a collection of code that can be imported into and used by other software. WPILib contains a set of useful classes and subroutines for interfacing with various parts of the FRC control system (such as sensors, motor controllers, and the driver station), as well as an assortment of other utility functions.
There are three versions of WPILib, one for each of the three officially-supported text-based languages: WPILibJ for Java, and WPILibC for C++, and RobotPy for Python. A considerable effort is made to maintain feature-parity between these languages - library features are not added unless they can be reasonably supported for both Java and C++ (with the C++ able to be wrapped by pybind for Python), and when possible the class and method names are kept identical or highly-similar. Java, C++, and Python were chosen for the officially-supported languages due to their appropriate level-of-abstraction and ubiquity in both industry and high-school computer science classes.
In general, C++ offers better high-end performance, at the cost of increased user effort (memory must be handled manually, and the C++ compiler does not do much to ensure user code will not crash at runtime). Java and Python offer lesser performance, but much greater convenience. Python users should take care to test their program to ensure that typos and other issues don't cause robot crashes, as Python is interpreted. New/inexperienced users are encouraged to use Java.
The primary documentation for WPILib is the FIRST Robotics Competition Control System Documentation.
WPILib is an open-source library - the C++ and Java source code is in the allwpilib mono-repo and python source code is in the mostrobotpy mono-repo. The Java and C++ source code can be found in the WPILibJ and WPILibC source directories:
While users are strongly encouraged to read the source code to resolve detailed questions about library functionality, more-concise documentation can be found on the official documentation pages for WPILibJ and WPILibC and RobotPy:
WPILib has a unified installer. See the WPILib Installation Guide for step-by-step installation instructions.
