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 · 2014-11-14 22:31:56Z

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, 2014 at 22:31

answered Apr 3, 2013 at 0:04

Reimeus

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1 Comment

chrisinmtown Over a year ago

Can the jython script return a value to the enclosing java program, received as the result of the eval() method?

Erik Pilz · Accepted Answer · 2013-04-02 23:47:59Z

0

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

answered Apr 2, 2013 at 23:47

Erik Pilz

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1 Comment

Matthias Over a year ago

exec does not solve the problem, then I receive the following SyntaxError: no viable alternative at character '''

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