Pyomo is a collection of Python software packages for formulating optimization models. Pyomo was developed by William Hart and Jean-Paul Watson at Sandia National Laboratories and David Woodruff at University of California, Davis. Significant extensions to Pyomo were developed by John Siirola at Sandia National Laboratories and Carl Laird at Purdue University. Pyomo is an open-source project that is freely available, and it is licensed with the BSD license. Pyomo is developed as part of the COIN-OR project. Pyomo is a popular open-source software package that is used by a variety of government agencies and academic institutions.