Pathway Tools is implemented using the Common Lisp (CL) programming language, but the PythonCyc package creates a bridge between Python and CL. That is, the PythonCyc package allows you to interact with Pathway Tools using the Python language. With PythonCyc you can write Python programs to execute Pathway Tools metabolic models, as well asto extract and modify data stored in Pathway/Genome Databases (PGDBs). It is also possible to call from Python many functions defined in Pathway Tools that manipulate genes, pathways, reactions, proteins, and more.