Pysolar is a Python library for calculating the position of the sun relative to the earth as a function of latitude, longitude, and time. There is also code included for other problems related to the development of photovoltaic systems. Still in alpha.
This project is an initial reference implementation of the VSI-E protocol. The implementation has been done using the C/C++ language and is in the form of a re-useable library developed on the Linux platform.