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I am using Python 2.7 to develop my software. Although I sometimes go back to c++ for performance issues, I have come to appreciate the Python programming language very much and recommend trying it. Especially for astrophysics it is a good choice due to the growing number of astronomy organizations and astrophysicists using it.
Stefan Czesla of the Hamburger Sternwarte is developing PyAstronomy, a "collection of astronomy related packages". It is a useful source for all different kinds of methods used in astrophysical research and provides a very convenient function fitting interface (with the choice of MCMC). I absolutely recommend it and encourage everybody to try it out.
I occasionally contribute code to this project myself. If you can provide anything you think is good and still missing in PyAstronomy, do not hesitate to contact Stefan.
Another library I like to use is PyEphem. I usually use it for coordinate transformations and getting the positions of Sun, Moon, and planets in the sky. It is a great package, be sure to check it out.