Announcing Release of Pyomo 4.0

We are pleased to announce the release of Pyomo 4.0 (4.0.9629). Pyomo is a collection of Python software packages that supports a diverse set of optimization capabilities for formulating and analyzing optimization models.

This release rebrands Coopr as Pyomo, which reflects the fact that users have consistently confused the Coopr software and the Pyomo modeling language.  Pyomo 4.0 includes the following significant changes:

  • Pyomo provides a single source tree replacing all Coopr packages
  • The 'pyomo' command replaces the 'coopr' command
  • The 'pyomo solve' subcommand replaces the former 'pyomo' command
  • The 'pyomo.environ' package is now used to import core Pyomo capabilities
  • Robust support for Python 3.x

The following are highlights of this release:

  • Modeling
    • Added a RealInterval domain
    • Major rework of coopr.dae. Can now represent higher order and partial differential equations. Also added more discretization schemes.
  • Solvers
    • Added preliminary support for a Benders solver
    • Added support for the BARON solver
    • Preliminary support for MPEC solvers, including the PATH solver
  • Transformations
    • Added explicit support for model transformations
    • The 'pyomo solve --transform' option specified model transformations
    • Created a streamline linear dual transformation
  • Other
    • The 'pyomo help' command documents installed capabilities
    • Major rework and simplification of the 'pyomo_install' script
    • Added support for parallelism using Pyro4

See for installation options and documentation for getting started with Pyomo.


  • Pyomo Developer Team

About Pyomo

The Pyomo home page provides resources for Pyomo users:

Pyomo development is hosted by Sandia National Laboratories and COIN-OR:

See the Pyomo Forum for online discussions of Pyomo: