Re: [Jython-users] Question about compiling with Jython

[Ted L. F. <te...@pr...>]

Hi, Jeff.

Another list member replied directly yesterday with this answer, which solved my issue:

java -cp /opt/jython2.7.0/jython.jar:. HelloWorld\$py

I needed the full path to the jar as well as the ":." to include the current working directory.

And you're right that the classpath must come first. Several examples I tried all worked, even just a single print statement. So it must not be a requirement to have a main() in the Python script itself.

Thanks for your analysis.

Ted

PS. I didn't realize until now that the message I referred to above had not been cc'ed to this list.

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Monday, October 1, 2018 12:02 PM, Jeff Allen <ja...@fa...> wrote:

> Hi Ted.
>
> Can you put the classpath at the end like that? Last thing is usually the class. Although why is java not complaining about main? Possibly it thinks HelloWorld$py is an inner class. Or is the $py being treated as a variable="" by the shell. It hardly matters: it still has to be a class that contains a main(), and one compiled from Python does not.If you want to see what it contains, you can javap it.
>
> You can make a class you run like that, but you have to write it in Java, and reference the .py file, or maybe have the text of the program in there as a string. It would be something like this:
>
> package demo_jython;
>
> import org.python.util.PythonInterpreter;
>
> public class ListDemo {
>
>     public static void main(String[] args) {
>         PythonInterpreter interp = new PythonInterpreter();
>         interp.exec("print 6*7");
>         interp.execfile("HelloWorld.py");
>     }
> }
>
> You would then run that in the normal way for a Java program, except you need the dependencies on the path, say by putting the jython.jar or jython-standalone.jar on the class path.
>
> Jeff Allen
>
> On 30/09/2018 20:05, Ted Larson Freeman wrote:
>
>> Hi, Jeff and Adam.
>>
>> Thanks for your replies. My goal is to see if I can produce a Java .class file using Jython, which can then be run using Java on the command line. A coworker was able to do this with Scala in less than 15 minutes (including installation), and I wanted to see if I could do the same thing with Jython. (I can run Jython itself with the script below just fine.)
>>
>> I'm still missing something, as I get the same error with either the CLASSPATH evironment variable or when explicitly setting it on the command line. For example:
>>
>> % ls
>> HelloWorld.py  HelloWorld$py.class
>> % java HelloWorld$py -classpath /home/ted/jython2.7.0
>> Error: Could not find or load main class HelloWorld
>>
>> Any further suggestions are greatly appreciated.
>>
>> Thanks!
>>
>> Ted
>>
>> PS. In case it helps, here is some info on my environment:
>>
>> % jython --version
>> Jython 2.7.0
>> % java -version
>> openjdk version "1.8.0_171"
>> OpenJDK Runtime Environment (build 1.8.0_171-8u171-b11-0ubuntu0.17.10.1-b11)
>> OpenJDK 64-Bit Server VM (build 25.171-b11, mixed mode)
>> % uname -srv
>> Linux 4.13.0-46-generic #51-Ubuntu SMP Tue Jun 12 12:36:29 UTC 2018
>>
>> Sent with [ProtonMail](https://protonmail.com) Secure Email.
>>
>> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
>> On Sunday, September 30, 2018 10:51 AM, Jeff Allen [<ja...@fa...>](mailto:ja...@fa...) wrote:
>>
>>> The normal way to use Jython would be like CPython:
>>>
>>> $ jython HelloWorld.py
>>>
>>> That's with an appropriate PATH, of course, or you say explicitly where the launcher is as part of the command. If you just wanted to run the the Python code, that would be the way. The compiled $py.class would only ever live in memory.
>>>
>>> But maybe you know this and have something more complicated in mind. You can run the class you made from a Java program (class with main()) that you write. But you could run the .py file from a Java program too, and I think more easily. Either way, you need the jython JAR on the path as Adam says. What do you have in mind that makes you want to compile it as a separate step like this?
>>>
>>> Jeff Allen
>>>
>>> On 29/09/2018 21:13, Ted Larson Freeman via Jython-users wrote:
>>>
>>>> I have just installed Jython 2.7, and am looking for a simple example of compiling a Python script down to a Java .class file. Following a suggestion on Stack Overflow, I tried to compile a file called HelloWorld.py, which contains this:
>>>>
>>>> class HelloWorld(object):
>>>>     def hello(self):
>>>>         print 'Hello, World!'
>>>>
>>>> if __name__ == '__main__':
>>>>     h = HelloWorld()
>>>>     h.hello()
>>>>
>>>> Using these Jython commands (in the same working directory):
>>>>
>>>> import py_compile
>>>> py_compile.compile('HelloWorld.py')
>>>>
>>>> That produces a file called HelloWorld$py.class, but when I try to run it with java from the command line, I get this error:
>>>>
>>>> Error: Could not find or load main class HelloWorld
>>>>
>>>> Please let me know what commands I should use.
>>>>
>>>> Thanks.
>>>>
>>>> Ted