PyCO2SYS is a Python implementation of CO2SYS, based on the MATLAB v2.0.5 but also including the updates made for tentatively forthcoming MATLAB v1.21 as well as some additional related calculations. This software calculates the full marine carbonate system from values of any two of its variables.
Every combination of input parameters has been tested, with differences in the results small enough to be attributable to floating point errors and iterative solver endpoint differences (i.e. negligible). See the scripts in the compare directory to see how and check this for yourself.