=== Explanation ===
The Java implementation of Python is limited in functionality. One can use the [https://docs.python.org/2/library/index.html standard library], but it's not possible to install additional Python modules. Moreover a growing number of projects build on
Python 3 which is not fully compatible with Python 2 Jython is based on. If you want to start learning Python it's recommended to learn Python 3.x instead of Python 2.
Even with the given limitations Jython is a powerful language for ImageJ scripting. Hopefully the examples on this page can convince you of that.