In 2014, the Policy Simulation Library [1] added a model called Tax-Simulator [2], which is a Python reimplementation of TAXSIM [3][4]. It is available as open-source [5], and designed to let researchers both change existing policy variables and implement new tax reforms in Python.
[1] https://pslmodels.org/
[2] https://taxcalc.pslmodels.org/
[3] https://taxcalc.pslmodels.org/about/history.html
[4] https://github.com/PSLmodels/Tax-Calculator/blob/master/taxc...
[5] https://github.com/PSLmodels/Tax-Calculator