Pyperplan is a lightweight STRIPS planner written in Python. Please note that Pyperplan deliberately prefers clean code over fast code. It is designed to be used as a teaching or prototyping tool. If you use it for paper experiments, please state clearly that Pyperplan does not offer state-of-the-art performance. It was developed during the planning practical course at the University of Freiburg during the winter term 2010/2011 and is published under the terms of the GNU General Public License 3 (GPLv3). Pyperplan supports the following PDDL fragment: STRIPS without action costs.