How to execute if statement using Jython

Question

import org.python.util.PythonInterpreter;
public class JythonTest {
public static void main(String[] args) {
    PythonInterpreter interp = new PythonInterpreter();
    interp.exec("if 2 > 1:");
    interp.exec("   print('in if statement!'");
}
}

I need to be able to execute Python code from a Java program, so decided to try out Jython, but I'm unfamiliar with it. I tried executing the above code, but got the error: "Exception in thread "main" SyntaxError: ("mismatched input '' expecting INDENT", ('', 1, 9, 'if 2 > 1:\n'))". Any ideas what this means or how I can otherwise execute an if statement using the PythonInterpreter?

I have a suggestion for you just hold on a second while I post another answer. — Malik Brahimi
– Malik Brahimi, Commented Feb 1, 2015 at 17:26

Malik Brahimi · Accepted Answer · 2015-02-01 17:04:34Z

1

Conditionals must be entered as a single string and you have an extra parenthesis:

import org.python.util.PythonInterpreter;

public class JythonTest {
    public static void main(String[] args) {
        PythonInterpreter interp = new PythonInterpreter();
        interp.exec("if 2 > 1: print 'in if statement!'");
    }
}

answered Feb 1, 2015 at 17:04

Malik Brahimi

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Comments

Malik Brahimi · Accepted Answer · 2015-02-01 18:31:29Z

0

Rather than executing a script line by line with strings you can invoke the interpreter to run a file. All you have to do is provide a file path to your python file, in this example place script.py in the src folder.

script.py

if 2 > 1:
    print 'in if statement'

JythonTest.java

import org.python.util.PythonInterpreter;

public class JythonTest {
    public static void main(String[] args) {
        PythonInterpreter interp = new PythonInterpreter();
        interp.execfile("src/script.py");
    }
}

edited Feb 1, 2015 at 18:31

answered Feb 1, 2015 at 17:29

Malik Brahimi

16.8k7 gold badges46 silver badges76 bronze badges

12 Comments

Makoto Over a year ago

Why would you add a new answer instead of editing it into your existing one?

Malik Brahimi Over a year ago

Because they're two separate ideas. Why do you think stack exchange would add such a feature?

Louis Slater Over a year ago

If I do this, will I be able to input to the program whilst it is running e.g for a python program like this: name=raw_input() print('Hi '+name) If so, how?

Louis Slater Over a year ago

Just tried the following code: link And got the error: Exception in thread "main" SyntaxError: ("no viable alternative at input '='", ('test1.py', 1, 10, 'print(name=raw_input()\n'))".

Malik Brahimi Over a year ago

That's not even proper python. You have two statement in a print statement.

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