Simulation tools
1. PyOPUS
A Python library to interface with some circuit simulators. It allows to use simulations from Python programs.
1.1. Links
2. Modelica
It is a formal object oriented language to describe systems and their behavior usinf equations and algorithms. There are a bunch of tools to process descriptions and obtain simulations and other results.
2.1. Links
2.2. Docs
Cellier, Clauß and Urquïa, Electronic Circuit Modelling and Simulation in Modelica, Proc. of EUROSIM 2007. http://www.euclides.dia.uned.es/aurquia/Files/Cellier_Eurosim_07.pdf