From jpype-project/jpype#1071 (comment) :

In theory Java and Python have compatible definitions of strings. Both are immutable and thus one should just be able to wrap a Java string as a Python string and be done. However, Strings are not a protocol but rather concrete objects, thus I can't just implement an interface for the C API of Python string and make them compatible. This failing forces either immediate conversion (which itself is problematic if a string is very large and the user does not intend to work with in Python extensively), or use a conversion. This problem does not just affect Java wrappers, but Qt wrappers and many other language bindings where immutable strings are available.