There are many more resources outside the scope of this tutorial that may be useful to you. Some of these are ATLAS-specific, and some are more general-purpose. We have compiled some resources here that you may find useful as you continue to learn.
The ATLAS Computing and Software TWiki [Internal] is the go-to resource for all things related to computing in ATLAS.
The ATLAS C++ coding guidelines is crucial in making sure that our code remains easily readable (and therefore extendable) by the collaboration. The guidelines should be followed if you are developing C++ for use in Athena.
The following are some useful ATLAS-specific tutorials.
The HEP Software Foundation and IRIS-HEP have several trainings available. Topics include: C++, CMake, CI/CD, Docker, version control, python, machine learning, uproot, and many more.
Take a look at the HSF Curriculum page for links to these trainings.
The PyHEP working group (from HSF) brings together a community of developers and users of Python in Particle Physics, with the aim of improving the sharing of knowledge and expertise. A collection of community-driven and community-oriented Python libraries providing HEP at large with an ecosystem for data analysis in Python can be found within the Scikit-HEP project.