For some java libraries I believe that it is an interface issue – libraries that modify fields ( and some forms of callbacks and reflection, I think?) aren’t correctly exposed from jython to the mode due to the architecture. See the FAQ for some discussion.
Some libraries such as Ani require you to specify a variable name for animation. Unfortunately they cannot access Python variables directly (and Java’s built in classes are immutable). To solve this problem we instead create a mutable
PrimitiveFloatobject. This object has a field.value, which you can use for these purposes. GitHub - jdf/processing.py: Write Processing sketches in Python
and the wiki
Some libraries–those that depend on certain functions being defined in your sketch–will not work. As we become aware of those, we will try to work with the authors of those libraries to make the design compatible with Python Mode, or at least to provide workarounds. GitHub - jdf/processing.py: Write Processing sketches in Python