  The Cherenkov Telescope Array (CTA) observatory will probe the non-thermal
universe above 20 GeV up to several hundreds of TeV with a significant
improvement in sensitivity and angular resolution compared to current
experiments. Its outstanding capabilities will allow to increase the number of
extragalactic cosmic accelerators detected at very high energy (VHE) and
therefore to better constrain the population of VHE accelerators and the
gamma-ray absorption processes in the intergalactic medium. For the first time
in the history of imaging atmospheric Cherenkov telescopes (IACTs), CTA will be
an open observatory and high-level data will be made available to the
astronomical community. Gammapy is an open-source Python package developed by
the Cherenkov telescope community that provides tools to simulate the gamma-ray
sky and analyse IACT data. The versatile architecture of, and steady user
contributions to Gammapy enable a large variety of high-level data analyses.
Examples of Gaammapy applications are presented, particularly in the context of
extragalactic science with CTA.
