Re: [Jython-dev] jythons module os

[Phil S. <phi...@ho...>]

Thanks Finn, I will try this stuff out sometime this week.

Jython _is_ more magical than I thought!

Finn Bock wrote:
> 
> >> >
> >> >I'm writing three tasks:
> >> >1) a jython task. This is like the ant <script> task
> >> >but it has several improvements:
> >> >   - handles indented jython scripts.
> >> >   - massages stack traces to make line numbers relative to
> >> >the ant build file, rather than relative to the start of the
> >> >script within the build file
> >
> >By the way, I gave up on figuring out how PyTracebacks work
> >(too many PyObjects)
> 
> The trick is never to trust what you see when calling
> System.out.print(). Some of the classes in the exception & traceback
> subsystem override toString().
> 
> >and ended up doing a regex thing to
> >patch up the line numbers. Am I missing some critical
> >piece of information?
> 
> It turned out that jython is badly prepared for setting the start line
> numbers in a call to compile(). I have added for feature request about
> it, but until it is implementated you might be able to use the hack
> below.
> 
> >> jytaskdef would then call project.addTaskDefinition("MyTask", MyTask).
> >>
> >> So, how big is my misunderstanding?
> >
> >Well, I didn't think that you could call jython classes
> >directly from java...
> 
> A python class which extends a java class or java interface is a
> completely ordinary java class.
> 
> >ant needs to be able to load the class in a classloader
> 
> If the new task is added by project.addTaskDefinition(String,Class)
> there is no need to let ant do the loading of the class.
> 
> You can get hold of the new Task and use like this:
> 
>   PyObject newClass = interp.get("MyTask");
>   Object tmp = newClass.__tojava__(Class.class);
>   if (tmp != Py.NoConversion && Task.class.isAssignableFrom((Class) tmp) {
>      project.addTaskDefinition("MyTask", (Class)tmp);
>   }
> 
> >and call various setxxx methods
> >and then call execute.
> >
> >Maybe jython is even more magical than I thought?
> 
> regards,
> finn
> 
> public class x {
>     public static void main(String[] args) {
>         PythonInterpreter interp = new PythonInterpreter();
>         try {
>             // a syntax error
>             interp.exec(
>                 "if 1:\n" +
>                 "   a = 1\n" +
>                 "  b = 0\n");
>         } catch (PyException exc) {
>             fixAndPrintError(exc, 20);
>         }
> 
>         try {
>             // throws a NameError
>             interp.exec(
>                 "def foo():\n" +
>                 "   a = c\n" +
>                 "foo()\n");
>         } catch (PyException exc) {
>             fixAndPrintError(exc, 20);
>         }
>     }
> 
>     private static void fixAndPrintError(PyException exc, int startLine) {
>         System.out.println();
>         System.out.println("Traceback (innermost last):");
> 
>         if (exc instanceof PySyntaxError) {
>             PySyntaxError se = (PySyntaxError)exc;
>             se.instantiate();
>             int line = se.value.__getattr__("lineno").__int__().getValue();
>             int col = se.value.__getattr__("offset").__int__().getValue();
>             String text = se.value.__getattr__("text").toString();
>             String filename = se.value.__getattr__("filename").toString();
>             System.out.println("  File \""+filename+"\", line "+
>                                 (line+startLine));
>             if (text != null && text.length() != 0) {
>                 System.out.println("\t"+text);
>                 String space = "\t";
>                 for(int j=1; j<col; j++)
>                     space = space+" ";
>                 System.out.println(space+"^");
>             }
>             System.out.println("SyntaxError: " + exc.value.__getitem__(0));
>             return;
>         }
> 
>         PyTraceback tb = exc.traceback;
>         StringBuffer buf = new StringBuffer();
>         dumpStack(tb, buf, startLine);
>         System.out.print(buf);
> 
>         PyObject typeName;
>         if (exc.type instanceof PyClass) {
>             typeName = new PyString(((PyClass)exc.type).__name__);
>         } else {
>             typeName = exc.type;
>         }
> 
>         System.out.println(typeName + ": " + exc.value);
>     }
> 
>     private static String line(PyTraceback tb, int startLine) {
>         if (tb.tb_frame == null || tb.tb_frame.f_code == null)
>             return "  (no code object) at line "+
>                         (tb.tb_lineno + startLine)+"\n";
>         return "  File \""+tb.tb_frame.f_code.co_filename+
>             "\", line "+(tb.tb_lineno + startLine)+
>             ", in "+tb.tb_frame.f_code.co_name+"\n";
>     }
> 
>     public static void dumpStack(PyTraceback tb, StringBuffer buf,
>                                  int startLine) {
>         buf.append(line(tb, startLine));
>         if (tb.tb_next != Py.None && tb.tb_next != tb)
>             dumpStack((PyTraceback) tb.tb_next, buf, startLine);
>         else if (tb.tb_next == tb) {
>             buf.append("circularity detected!"+tb+tb.tb_next);
>         }
>     }
> 
> }
> 
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