Re: [Jython-users] NullPointerException error when calling a python method

[Robert W. B. <rb...@di...>]

Hello Hubert,

On Wed, 17 Oct 2001, Hubert Yoshizaki wrote:
<snip>
> still having problems...
>
> tried the 'import tryJythonSample'=A0 (without using the jythonc --pack=
age
> option)
>
> Exception in thread "main" java.lang.NullPointerException
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.PyJavaClass.lookup(PyJavaClass=
.java:39)
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.PyObject.<init>(PyObject.java:=
46)
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.PySingleton.<init>(PySingleton=
.java:8)
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.PyNone.<init>(PyNone.java:7)
> =A0=A0=A0=A0=A0=A0=A0 at
> org.python.core.PySystemState.initStaticFields(PySystemState.java:341
> )
> =A0=A0=A0=A0=A0=A0=A0 at
> org.python.core.PySystemState.initialize(PySystemState.java:320)
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.Py.initProperties(Py.java:665)
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.Py.initProxy(Py.java:709)
> =A0=A0=A0=A0=A0=A0=A0 at tryJythonSample.<init>(tryJythonSample.java:10=
5)
> =A0=A0=A0=A0=A0=A0=A0 at tryJythonMain.main(tryJythonMain.java:8)
>
> tried the 'import tryJythonSample.* when using the jythonc --package
> option.
> got the error
>
> C:\Hubert\Work\Projects\tryJython\tryJythonProject>java tryJythonMain
> Exception in thread "main" java.lang.NullPointerException
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.PyJavaClass.lookup(PyJavaClass=
.java:39)
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.PyObject.<init>(PyObject.java:=
46)
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.PySingleton.<init>(PySingleton=
.java:8)
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.PyNone.<init>(PyNone.java:7)
> =A0=A0=A0=A0=A0=A0=A0 at
> org.python.core.PySystemState.initStaticFields(PySystemState.java:341
> )
> =A0=A0=A0=A0=A0=A0=A0 at
> org.python.core.PySystemState.initialize(PySystemState.java:320)
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.Py.initProperties(Py.java:665)
> =A0=A0=A0=A0=A0=A0=A0 at org.python.core.Py.initProxy(Py.java:709)
> =A0=A0=A0=A0=A0=A0=A0 at
> tryJythonSample.tryJythonSample.<init>(tryJythonSample.java:107)
> =A0=A0=A0=A0=A0=A0=A0 at tryJythonMain.main(tryJythonMain.java:8)
>
>
> error wise, unless I'm mistaken, it seems to be running into the same
> problem each time
> Any ideas?
>
> Hubert

I'm not sure this helps, but the code you list below works fine for me
(linux+sunJDK1.3).  One thing that might be worth checking is whether
the tryJythonSample class actually exists in a file called
"tryJythonSample.py".  The matching classname/filename is required here,
and a difference in those names makes a NPE like you are seeing.

If that's no help, check back again :)

-robert

> (for others, here's the code...)
>
> import org.python.core.*;
> import tryJythonSample;
>
> public class tryJythonMain
> {
> public static void main(String[] args)
> {
> tryJythonSample jySample =3D new tryJythonSample();
> jySample.makeObject();
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0
> }
> }
>
> import java
> class tryJythonSample(java.lang.Object):
> =A0=A0=A0=A0=A0=A0=A0 def __init__(self):
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 "@sig public tryJythonSample()"
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 print "Constructor for tryJythonSampl=
e"
> =A0=A0=A0=A0=A0=A0=A0 def makeObject(self):
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 "@sig public void makeObject()"
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 print "I have just called a python me=
thod!!"
>
>
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