Wikipedia
PyChess
PyChess is a free software chess client developed for GNU. It allows users to play offline or online via the Free Internet Chess Server (FICS). PyChess also incorporates a built-in chess engine, which in contrast to most other chess AIs, is written in the Python language and focuses more on fun of play than raw strength. For more advanced users, PyChess allows for virtually any other external chess engine to be used with it.