Question

how can i iterate on a Jython PyList and cast or convert my contained object to java.lang.String ?

in this old tutorial, it is done by using __ tojava __ like :

(EmployeeType)employeeObj.__tojava__(EmployeeType.class);

i suppsoe this may be something like :

 PyList pywords = pythonFactoryCreatedObject.pythonMethodReturningPyList()

 int count = pywords.__len__();
 for (int idx = 0 ; idx < count ; idx++) {
     PyObject obj = pywords.__getitem__(idx);

    //here i do not know how to have a kind of 'String word = pywords[idx]' statement

    //System.out.println(word);
 }

is it also possible to have :

• a conversion from PyList to java Array or List ? so that the construct ‘for (String word : mylist) { }’ can be used ?

• i will have the same trouble with simple python dictionary mapping to an adequate java object, what will be the best mapping ?

Is there a tutorial doc on the java part usage of Jython ? i’m quite ok with python, but new to Java and Jython, and i found only documentation on the Java usage from Jython while i need to embed a Python module inside a Java framework…

best

Answer 1

PyList actually implements java.util.List<Object>, so you can use that directly from Java side.
If you fill with strings, its elements will be PyString (or maybe PyUnicode).
So:

List pywords = pythonFactoryCreatedObject.pythonMethodReturningPyList();
for (Object o : pyList){
  String string = ((PyString) o).getString();
  //whatever you want to do with it 
}

or

List pywords = pythonFactoryCreatedObject.pythonMethodReturningPyList()
for (Object o : pyList){
  String string = ((PyObject) o).__toJava__(String.class);
  //whatever you want to do with it 
}

whichever you find clearer.

Edit:
here’s the standard doc on embedding Jython into Java. The better way to use Jython from Java would be to implement Java interfaces from Jython and manipulate the interfaces from Java, but it seems you’re working with an existing Python codebase, so that wouldn’t work without some changes.