Greetings, I am very proud to announce the release of version 2.0 of ytree! ytree https://github.com/brittonsmith/ytree is tool for working with merger-tree data from multiple sources and for generating merger-trees from Gadget FoF/SUBFIND catalogs. For a brief example of using ytree on merger-tree data, have a look at this notebook https://github.com/brittonsmith/ytree/blob/master/doc/source/notebooks/Intro... . This is significant update to ytree in terms of both usability and speed. Updates include: - tree building and field i/o now occur on-demand resulting in a huge speedup. - support for yt-like derived fields that can be defined with simple functions. - support for yt-like alias fields allowing for universal field naming conventions to simplify writing scripts for multiple data formats. - support for analysis fields which allow users to save the results of expensive halo analysis to fields associated with each halo. - significantly improved documentation http://ytree.readthedocs.io/en/latest/ including a guide to adding support for new file formats. - all fields in consistent-trees and Rockstar now fully supported with units. - an optimized format for saving and reloading trees for fast field access. ytree can be installed with pip: pip install ytree or from source, by going to https://github.com/brittonsmith/ytree git clone https://github.com/brittonsmith/ytree cd ytree pip install -e . Full documentation can be found at http://ytree.readthedocs.io/. ytree is an open-source community project. Please help make it better with your contribution! Thanks! Britton