如何使用Jython执行if语句

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?

Answer 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!'");
    }
}

Answer 2

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");
    }
}