Re: compile, marshal, exec

On 11 May 2015, Alan Kennedy <[email protected]> wrote:
> [Fernando]
> > >>> f = file('dateGetYmd') # the script file, which has a namesake function
> > >>> obj = compile(f.read(), '', 'exec')
> > >>> marshal.dump(obj, fc)
> > >>> exec obj
> > >>> dateGetYmd('0') # this function call will also access local objects
> 
> > Would this work in Jython? docs would say so, but is there any caveats?
> 
> There should no problem with this. Obviously, the file containing the source must be acessible to the servlet context you are running it from.
> 
> You could execute the jython source listed above directly in an embedded jython interpreter, meaning you would represent it as a string, and pass it to the 'exec' method of a org.python.util.PythonInterpreter.
> 
> I am using pyservlet to call my own jython servlet and in here I would run the code above. I don't see the need for extra interpreters, right?


> Or you could figure out the equivalent java calls, and invoke them directly from java.
> 
> PyServlet gives a good example of how to write all the relevant code, in java.
> 
> I would use 'execfile' instead of 'compile', which applies to both java code and jython. Here is where PyServlet does it
> 
> <https://hg.python.org/jython/file/6855fa289d48/src/org/python/util/PyServlet.java#l208>
> 
> thks, I looked at it already but I don't have experience with java and its libraries. If I get a decently working solution then I could look into porting my jython servlet to java, but I am really not looking forward to it. For now I am merely seeing if there is any major roadblock.

The reason for 'compile' is to persist the byte code for a quicker startup. Sadly, marshall in jython does not seem to be working well.


> > and what about performance? what does compile return? (python byte codes?)
> 
> Compile (and exec and execfile) return JVM bytecode representing the jython source. The performance of running this code in an embedded context should be the same as running in a non-embedded context.
> 
> > Or is there a better way to do it?
> 
> Not necessarily better, but an alternative to using PyServlet is to use modjy, which would give you WSGI compatibility, and better configurability.
> 
> Alan.
> 
> Thanks for your extensice feedback Alan!

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