The PV_LIB Toolbox provides a set of well-documented functions for simulating the performance of photovoltaic energy systems. The toolbox was developed at Sandia National Laboratories. The toolbox is available in Matlab and Python versions. Download links are are shown for both below.
2018 Publication of PVLIB in Journal of Open Source Software: pvlib python: a python package for modeling solar energy systems (1082 downloads)