Invited talk I gave at Europython 2016. Cosmology is a big data challenge, that goes from the tecnological development of space satellites, to data processing to the interpretation of the data to test gravity and the evolution of the Universe, After an overview on Cosmology, I discuss the challenge of the Dark Universe and how we go from TB of data to six parameters. Extraction of cosmological parameters is done via MCMC simulations for which the MontePython by B.Audren&J.Lesgourges offers an open source code written in python (https://github.com/baudren/montepythonpublic). Python is also used to analyze chains or for visualization (see also http://cosmologist.info/cosmomc/readmepython.html by A.Lewis).