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

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Hi,<br>
I'm just experimenting with jythonc (new to Python/Jython and not really
experienced in Java either for that matter) and came up with this
problem.<br>
<br>
My python test code is simply this:<br>
<br>
<font color="#0000FF"><i>import java<br>
class tryJythonSample(java.lang.Object):<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; def __init__(self):<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&quot;@sig public tryJython()&quot;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; print
&quot;Constructor for tryJython&quot;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; def makeObject(self):<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&quot;@sig public void makeObject()&quot;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; print
&quot;I have just called a python method!!&quot;<br>
<br>
</font></i><font color="#000000">after doing a jythonc tryJythonSample.py
and get the corresponding class files and java file I created a java file
that calls the methods.<br>
My java file.<br>
<br>
</font><font color="#0000FF"><i>import tryJythonSample.*;<br>
import org.python.core.*;<br>
<br>
public class tryJythonMain<br>
{<br>
 public static void main(String[] args)<br>
 {<br>
  tryJythonSample jySample = new tryJythonSample();<br>
  jySample.makeObject();<br>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
 
 } 
}&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;
 
 
when I run my java file (tryJythonMain) I get the following: 
 
Exception in thread &quot;main&quot;
java.lang.NullPointerException 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; at
org.python.core.PyJavaClass.lookup(PyJavaClass.java:39) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; at
org.python.core.PyObject.&lt;init&gt;(PyObject.java:46) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; at
org.python.core.PySingleton.&lt;init&gt;(PySingleton.java:8) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; at
org.python.core.PyNone.&lt;init&gt;(PyNone.java:7) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; at
org.python.core.PySystemState.initStaticFields(PySystemState.java:341 
) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; at
org.python.core.PySystemState.initialize(PySystemState.java:320) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; at
org.python.core.Py.initProperties(Py.java:665) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; at
org.python.core.Py.initProxy(Py.java:709) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; at
tryJythonSample.&lt;init&gt;(tryJythonSample.java:105) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; at
tryJythonMain.main(tryJythonMain.java:9) 
 
Can anyone tell me what I'm doing
wrong? 
Is there a problem with dependencies? 
Or is it something really dumb and simple that tells me I'm simply too
tired to think properly? 
Any help would be greatly appreciated. 
Thanks, 
Hubert
 
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Thread: [Jython-users] NullPointerException error when calling a python method

jython-users