Jython SyntaxError (from Java app)

Question

In my Java app I want to use Jython to interpret Python code.
So I initialise Jython as follows:

PySystemState.initialize();
PythonInterpreter jython = new PythonInterpreter();

Then I want to test it like this:

jython.eval("out = ''");
jython.eval("out += 'Test1\n'");
jython.eval("out += 'Test2\n'");
System.out.println(jython.get("out").toString());

However, the first eval line throws this error:

  File "<string>", line 1
    out = ''
       ^
SyntaxError: mismatched input '=' expecting EOF

When I try it with exec instead of eval I get this error:

  File "<string>", line 2
    '
    ^
SyntaxError: no viable alternative at character '''

Any ideas what I am doing wrong here?

PS: I am using jython-2.5.4-rc1

Reimeus · Accepted Answer · 2014-11-14T22:31:56.250

2

You'll need to ensure you have the following

Declare an out variable
Because you're using Java, escape special characters such as \\n
Use exec rather than eval

This will produce:

PythonInterpreter jython = new PythonInterpreter();
jython.set("out", new PyString());
jython.exec("out = ''");
jython.exec("out += 'Test1\\n'");
jython.exec("out += 'Test2\\n'");
System.out.println(jython.get("out").toString());

edited Nov 14 '14 at 22:31

answered Apr 03 '13 at 00:04

Reimeus

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Can the jython script return a value to the enclosing java program, received as the result of the eval() method? – chrisinmtown Feb 25 '16 at 19:05

score 0 · Answer 2 · answered Apr 02 '13 at 23:47

0

You should use exec to execute statements. eval evaluates and returns a PyObject.

answered Apr 02 '13 at 23:47

Erik Pilz

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exec does not solve the problem, then I receive the following SyntaxError: no viable alternative at character ''' – Matthias Apr 02 '13 at 23:59

Jython SyntaxError (from Java app)

2 Answers2