jython-users — Discussion of and questions about using Jython

Re: [Jython-users] idea: custom tag library and jython

[Niko S. <ni...@na...>]

Ashish,

> How about developing a custom tag for web apps. One that takes
> jython scriplet in its body. The request, response, session etc
> would be available as explicit objects. The tag could embed a
> jython interpreter and execute the given code. How I wish jsp 
> were jython server pages!

very interesting you are mentioning this idea, i was thinking in 
the same lines just a few days ago (and didn't come back). But 
through your posting i just tried it out today: and it turns out 
that it is possible :) (even if it is a bit more extra effort):

creating just a straight forward jython class inherited from 
javax.servlet.jsp.tagext.TagSupport gave me a strange error 
message: "AttributeError: write-only attr: pageContext". Also with 
setting python.security.respectJavaAccessibility to false didn't 
help, so i had to write a Java class (derived from TagSupport) 
which provides an accessor method to pageContext. The Jython Custom 
Tag implementation has then to use this to get access to the 
PageContext object.

---- DemoTag.py ----
from java.io import IOException
from javax.servlet.jsp import JspTagException
from niko.test import JythonTagSupport

class DemoTag(JythonTagSupport):
    
    def doStartTag(self):
        try:
            out = self.pageContext.getOut()
            out.print("Hello World from Jython Tag.")
        except IOException, e:
            raise JspTagException("Input/output error: %s" % 
e.toString())
        # since this is an empty tag
        return self.SKIP_BODY

---- JythonTagSupport ----
package niko.test;

import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.TagSupport;

public class JythonTagSupport extends TagSupport {

  public JythonTagSupport() {
    super();
  }

  public PageContext getPageContext() {
    return pageContext;
  }
  
}
-----

Then the only two remaining steps are to define the new jython tag 
in your tag library descriptor file (TLD) and make sure that 
jython.jar is available to the classloader of your servlet 
container.

Happy jython-custom-tag-developing :-)
Niko

Re: [Jython-users] idea: custom tag library and jython

[Niko S. <ni...@na...>]

Ashish,

> How about developing a custom tag for web apps. One that takes
> jython scriplet in its body. The request, response, session etc
> would be available as explicit objects. The tag could embed a
> jython interpreter and execute the given code. How I wish jsp 
> were jython server pages!

very interesting you are mentioning this idea, i was thinking in 
the same lines just a few days ago (and didn't come back). But 
through your posting i just tried it out today: and it turns out 
that it is possible :) (even if it is a bit more extra effort):

creating just a straight forward jython class inherited from 
javax.servlet.jsp.tagext.TagSupport gave me a strange error 
message: "AttributeError: write-only attr: pageContext". Also with 
setting python.security.respectJavaAccessibility to false didn't 
help, so i had to write a Java class (derived from TagSupport) 
which provides an accessor method to pageContext. The Jython Custom 
Tag implementation has then to use this to get access to the 
PageContext object.

---- DemoTag.py ----
from java.io import IOException
from javax.servlet.jsp import JspTagException
from niko.test import JythonTagSupport

class DemoTag(JythonTagSupport):
    
    def doStartTag(self):
        try:
            out = self.pageContext.getOut()
            out.print("Hello World from Jython Tag.")
        except IOException, e:
            raise JspTagException("Input/output error: %s" % 
e.toString())
        # since this is an empty tag
        return self.SKIP_BODY

---- JythonTagSupport ----
package niko.test;

import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.TagSupport;

public class JythonTagSupport extends TagSupport {

  public JythonTagSupport() {
    super();
  }

  public PageContext getPageContext() {
    return pageContext;
  }
  
}
-----

Then the only two remaining steps are to define the new jython tag 
in your tag library descriptor file (TLD) and make sure that 
jython.jar is available to the classloader of your servlet 
container.

Happy jython-custom-tag-developing :-)
Niko

Re: [Jython-users] idea: custom tag library and jython

[Niko S. <ni...@na...>]

Ashish,

> How about developing a custom tag for web apps. One that takes
> jython scriplet in its body. The request, response, session etc
> would be available as explicit objects. The tag could embed a
> jython interpreter and execute the given code. How I wish jsp 
> were jython server pages!

very interesting you are mentioning this idea, i was thinking in 
the same lines just a few days ago (and didn't come back). But 
through your posting i just tried it out today: and it turns out 
that it is possible :) (even if it is a bit more extra effort):

creating just a straight forward jython class inherited from 
javax.servlet.jsp.tagext.TagSupport gave me a strange error 
message: "AttributeError: write-only attr: pageContext". Also with 
setting python.security.respectJavaAccessibility to false didn't 
help, so i had to write a Java class (derived from TagSupport) 
which provides an accessor method to pageContext. The Jython Custom 
Tag implementation has then to use this to get access to the 
PageContext object.

---- DemoTag.py ----
from java.io import IOException
from javax.servlet.jsp import JspTagException
from niko.test import JythonTagSupport

class DemoTag(JythonTagSupport):
    
    def doStartTag(self):
        try:
            out = self.pageContext.getOut()
            out.print("Hello World from Jython Tag.")
        except IOException, e:
            raise JspTagException("Input/output error: %s" % 
e.toString())
        # since this is an empty tag
        return self.SKIP_BODY

---- JythonTagSupport ----
package niko.test;

import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.TagSupport;

public class JythonTagSupport extends TagSupport {

  public JythonTagSupport() {
    super();
  }

  public PageContext getPageContext() {
    return pageContext;
  }
  
}
-----

Then the only two remaining steps are to define the new jython tag 
in your tag library descriptor file (TLD) and make sure that 
jython.jar is available to the classloader of your servlet 
container.

Happy jython-custom-tag-developing :-)
Niko

Re: [Jython-users] Swing examples

[BillWorker 2. <bil...@in...>]

Let me explain myself!

In Java if I were to extend AbstractListModel and use an array internalArray
to hold my data internally, then for getElementAt() I could do
internalArray[i]. The object that I get from the array does not need to be
converted to java.lang.Object as it ALWAYS inherits from java.lang.Object

However, in Jython I have to either
i. ensure that the object that I get from the array (list) is an instance of
java.lang.Object or
ii. wrap the Python object into a wrapper class that inherits from
java.lang.Object

This is not obivous to a new Jython programmer who has come from Java!

Ashish

[Jython-users] idea: custom tag library and jython

[BillWorker 2. <bil...@in...>]

Just wondering if it is a good idea!

How about developing a custom tag for web apps. One that takes jython
scriplet in its body. The request, response, session etc would be available
as explicit objects. The tag could embed a jython interpreter and execute
the given code. How I wish jsp were jython server pages!

Ashish

[Jython-users] Looking for Jython promo materials

[Brad C. <bk...@mu...>]

Next week I need to give a one hour presentation at Novell's Brainshare titled:

"Rapid Application Development with Jython".

I'll be demo'ing Jedit, JythonInterpreter (plugin), JinSitu and of course Jython, on Win32 
and NetWare Systems.

I have a simple Beans based application that I'll be showing, but I'm looking for some 
other things:

1. Quick intro to the Python Language (10 minutes)

2. Perhaps a Power Point slide show for item 1

3. Quick examples that I can type interactively that demonstrate the power of the 
interpreted, typeless nature of Jython.

I'm aware of what's available at python.org and jython.org, but if you have any other 
recommendations I'd appreciate it.

My audience will be in-experienced VB'ers/Perlers.. And experienced Java developers.

Thanks for any suggestions,




Brad Clements,                bk...@mu...   (315)268-1000
http://www.murkworks.com                          (315)268-9812 Fax
AOL-IM: BKClements

Re: [Jython-users] Jython 2.1 on NetWare - IOError Wrong Kind of Object

[Brad C. <bk...@mu...>]

Sorry, false alarm.

It was a NetWare thing. I needed to tell java to create a console for I/O.

java -ns ...


Brad Clements,                bk...@mu...   (315)268-1000
http://www.murkworks.com                          (315)268-9812 Fax
AOL-IM: BKClements

[Jython-users] Jython 2.1 on NetWare - IOError Wrong Kind of Object

[Brad C. <bk...@mu...>]

Nothing like waiting to the last minute..

I have to demo Jython at Novell's Brainshare next week. Working well on Win32, and if 
I pass command line args on NetWare .. it seems to work (for swing apps)

But if I want to run it interactively, I get 

>>> Traceback 
   (no code object) at line 0

IOError: Wrong kind of object

--

Could be from a number of causes, anyone know which is most likely?

1. reading from stdin returned EOF right away? I'm not sure if stdin is working

2. When  I installed it, I used the graphical install and specified OS = Macintosh. Hey, it 
installed! But, is there perhaps an os. specific class that is being used for interactive I/O 
and it's making mac specific calls?




Brad Clements,                bk...@mu...   (315)268-1000
http://www.murkworks.com                          (315)268-9812 Fax
AOL-IM: BKClements

[Jython-users] Donald Hagan/KC-CORPSVC/KC/FRS is out of the office.

[<don...@kc...>]

I will be out of the office starting  03/14/2002 and will not return until
03/18/2002.

[Jython-users] JavaOne

[Oti <oh...@ya...>]

Hello,

is somebody going to JavaOne ?
Oti.

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[Jython-users] jython for a large-scale web site?

[Sandy N. <san...@ho...>]

Hi folks,

I work with a web company that has about 180,000 registered users, and
pretty good weekly traffic stats. Their current platform of
development includes Oracle for the data server, AOLServer for web
serving platform and TCL to script the whole thing together, with
everything running on Solaris on a few fat multiprocessor Sun
machines.

I just had a chat with the CTO (I've been trying to get him to look
into python for a while) and it seems his resistance has finally
broken (-: he spent a real weekend with the python and his initial
misgivings about significant whitespace have disapeared, and now he's
raving about how well the language 'flows'.

Suddenly, this recent convert wants to incorporate python into the
next generation build of the web site. Now he is leaning towards using
a combination of jython and java to reimplement and refactor the
design as he likes the support and momentum behind java and doesn't
want to give up the productivity benefits of a scripting language.

Now, I'm really happy to have turned the top tech decision-maker in
the company on to python (kinda validates my fascination with the
language internally :-) But I'm worried about things like performance
and scalability: is it wise to service this number of customers with
jython servlets running on tomcat for example?

Any advice would be much appreciated.

Thanks.

Sandy

<cross-posted to c.l.py>

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[Jython-users] |±¤-°í| 21¼¼±âÇü ¿µ¾î °øºÎ¹ýÀ» ÁغñÇϼ¼¿ä

[(ÁÖ)¾¾Äß½º <se...@se...>]

<html>
<head>
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<title>신제품 출시</title>
</head>
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        <p align="left" style="MARGIN-LEFT: 4px; LINE-HEIGHT: 120%">
        <font color="#111111" size="2">안녕하십니까? <br>
        DM Academy의 웹지기 입니다.<br>
        </font><font face="굴림체" size="2" color="#111111">'봄의 기운이 일어섰다' 는 입춘,'숨어서 
        겨울잠을 자던 동물들이 놀라서 떠든다' 는 경칩을 모두 지나쳤습니다. 이제는 바람의 숨결조차 향긋하게 느껴집니다. &nbsp;<br>
        봄이 오는 
        즐거움을 알게 해준 겨울이 이제 밉지 만은 않습니다.<br>
        길거리 꽃집에라도 들러, 성급하게 피어난 프리지어 한 다발을 사서 봄 마중을 가야겠습니다.<br>
        오늘은 봄소식같이 반가운, 신작 소식을 알려드립니다.</font></p></td>
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        <td width="67%" height="208">&nbsp;
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        <p align="left">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
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       <td width="574">
       <p style="LINE-HEIGHT: 150%"><font color="#111111">&nbsp;<FONT size=2>jyt...@li...님</FONT><font style="FONT-SIZE: 9pt">귀하의 
       승락없이 홍보성 전자 우편을 보내게 된 점 정중히 사과 드립니다.<br>
       &nbsp;정보통신망이용촉진법 규정을 준수하여 </font><font color="#ff0000">
       <span style="FONT-SIZE: 9pt">광고</span></font><span style="FONT-SIZE: 9pt">메일임을 
       표시하였으며, 수신거부 장치를 마련하고 <br>
       &nbsp;있습니다. 귀하의 전자 우편 주소는 인터넷 상의 공개된 장소에서 습득하였으며, 저희는 귀하의<br>
       &nbsp;전자우편 주소 외 어떠한 개인정보도 가지고 있지 않으므로 안심하시기 바랍니다. 수신을 원치<br>
       &nbsp;않으시면 <font color="#ff0000">수신거부</font>를 클릭해 주십시요</span></font></p></td>
     </tr>
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Re: [Jython-users] embedding questions

[Paul G. <pau...@so...>]

Here is a variation on the method described below. It assumes that you 
have the python code that defines your methods stored in a Sting. This 
allows you to retrieve the function definitions  from a database, 
resource, hardcoded string, etc.


       static final  String code = "def helloWorld():\n   print 'Hello 
World\n'";   // example using a hardcoded string

....

       interp_ = new InteractiveConsole();
       code = code.trim();
        StringTokenizer st = new StringTokenizer
            (code, System.getProperty("line.separator"));
        while (st.hasMoreTokens())
        {
            String lineOfCode = st.nextToken();
            interp_.push(lineOfCode);
        }

....


-Paul




>>- I would also like to expose some python functions into the global
>>namespace of any executed python script.  These functions are actually
>>implemented in Java and provide some app-specific functionality to the
>>python environment. 
>>
>
>I'm not one of the 'experts', but this is how I do it and it seems to work=
> fine; just 'execfile' the file with the functions:
>
> InputStream functionFileStream =3D FileIO.FindFileOrStream(=
> functionListName, dataPath, "functions", debugLevel);
> python.execfile( functionFileStream, functionListName); // pass the name=
> for parsing errors
>
>This way the names are scoped into the top level.
>
>(My 'FindFileOrStream' finds the function file in a file or jar in the=
> 'dataPath'. I have a list of functions files in an XML configuration=
> file.)
>
>- Jim
>
>

-- 
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Technoparkstrasse 1, CH-8005 Zurich. Email: pau...@So...

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RE: [Jython-users] Help please! -- Regarding jythonc use

[TigerWraith <tig...@ks...>]

Also I just saw how I typed that, im not trying to be rude. Just trying to
reclaim my computer back from what my GF did to it today. And she wonders
why she's locked out of it.

Sorry if it seems im being rude.

TigerWraith

RE: [Jython-users] Help please! -- Regarding jythonc use

[TigerWraith <tig...@ks...>]

And just where im I typing this script at?

Re: [Jython-users] Help please! -- Regarding jythonc use

[chuck c. <cc...@zi...>]

If you write a simple jython script and play with jythonc a little bit I
think you'll come to understand the various options pretty quickly.  I
started using jythonc today for the first time and with a little
experiementation I had it doing everything I wanted.

To start with create a simple jython script.

jythonc MyPy.py
This will create a java file in the jpywork directory and will also compi=
le
it to a class file.  This will just process the module that you pass in.

jythonc -c MyPy.py
This becomes helpful if you write jython that makes use of the .py module=
s
found in the Lib directory of your jython install.  For instance, if you
import and use the cPickle module you'll notice that when jythonc says it=
 is
creating a .java file you'll see MyPy module as well as copy_reg module.
This is because cPickle imports copy_reg.  So in this way you can build
everything in the core library to java so you won't need the have your
python.home variable set and have all of thos files in Lib.

jython -c -j MyJar.jar MyPy.py
This will compile all the files you need into one nice and tidy jar file =
and
you can then execute your code using java -jar MyJar.jar

if you are importing lots of java files you have written in
com.company.project.subsystem.* then you can add these pacakages using
the -A option.  You can include multiple packages using a comma separated
list.

Try it out.  I'm sure just these couple of commands will get you pretty f=
ar.

One minor cosmetic bug in jythonc....
If you type jythonc the Usage message was never updated during the migrat=
ion
from jpython -- it still says jpythonc

chuck
----- Original Message -----
From: "TigerWraith" <tig...@ks...>
To: <jyt...@li...>
Sent: Wednesday, March 13, 2002 10:16 PM
Subject: RE: [Jython-users] Help please!


> Ok I'm using win2K Pro how in do I get it to compile can anyone please
tell
> me how. The examples aren't very good references for me.
>
> -----Original Message-----
> From: jyt...@li...
> [mailto:jyt...@li...]On Behalf Of Gerhard
> H=E4ring
> Sent: Wednesday, March 13, 2002 8:01 PM
> To: jyt...@li...
> Subject: Re: [Jython-users] Help please!
>
>
> Le 13/03/02 ? 20:47, TigerWraith =E9crivit:
> > Can jython compile python files into class files for java?
>
> Sure. jythonc does this.
>
> Gerhard
> --
> mail:   gerhard <at> bigfoot <dot> de       registered Linux user #6423=
9
> web:    http://www.cs.fhm.edu/~ifw00065/    OpenPGP public key id 86AB4=
3C0
> public key fingerprint: DEC1 1D02 5743 1159 CD20  A4B6 7B22 6575 86AB 4=
3C0
> reduce(lambda x,y:x+y,map(lambda
> x:chr(ord(x)^42),tuple('zS^BED\nX_FOY\x0b')))
>
> _______________________________________________
> Jython-users mailing list
> Jyt...@li...
> https://lists.sourceforge.net/lists/listinfo/jython-users
>
>
>
> _______________________________________________
> Jython-users mailing list
> Jyt...@li...
> https://lists.sourceforge.net/lists/listinfo/jython-users

RE: [Jython-users] Help please!

[TigerWraith <tig...@ks...>]

Ok I'm using win2K Pro how in do I get it to compile can anyone please tell
me how. The examples aren't very good references for me.

-----Original Message-----
From: jyt...@li...
[mailto:jyt...@li...]On Behalf Of Gerhard
Häring
Sent: Wednesday, March 13, 2002 8:01 PM
To: jyt...@li...
Subject: Re: [Jython-users] Help please!


Le 13/03/02 ? 20:47, TigerWraith écrivit:
> Can jython compile python files into class files for java?

Sure. jythonc does this.

Gerhard
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Re: [Jython-users] Help please!

[Gerhard <gh_...@gm...>]

Le 13/03/02 ? 20:47, TigerWraith écrivit:
> Can jython compile python files into class files for java?

Sure. jythonc does this.

Gerhard
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mail:   gerhard <at> bigfoot <dot> de       registered Linux user #64239
web:    http://www.cs.fhm.edu/~ifw00065/    OpenPGP public key id 86AB43C0
public key fingerprint: DEC1 1D02 5743 1159 CD20  A4B6 7B22 6575 86AB 43C0
reduce(lambda x,y:x+y,map(lambda x:chr(ord(x)^42),tuple('zS^BED\nX_FOY\x0b')))

[Jython-users] Help please!

[TigerWraith <tig...@ks...>]

Can jython compile python files into class files for java?

Re: [Jython-users] embedding questions

[Ype K. <yk...@xs...>]

Josh,

>Hello all,
>	I'm working to embed jython within an in-house distributed java
>application.  I'm really looking to solve two major problems and haven't
>come to any answers from looking over the javadoc or the source code.
>
>- I need a hook into the import functionality of the interpreter.  We store
>scripts in JAR files that are 'hot-pluggable' into a running system, so when
>interpreting a python script that imports another module, I would like to be
>able to handle such an event so that I may look through these
>'hot-pluggable' JAR files instead of relying on the sys.path or PYTHONPATH
>variables.

Have a look at imp.java in the org/python/core directory.
At the end is the java class you need to replace/enhance.
It's possible to do that from both jython code and java code
by hooking the built in.

Iirc there is work going on on importing from jars.
You might ask on jython-dev.

<rest already answered>

Have fun,
Ype

-- 

Re: [Jython-users] embedding questions

[Jim A. <ji...@tr...>]

On 3/13/2002 at 11:27 AM Seabloom, Josh wrote:

>- I would also like to expose some python functions into the global
>namespace of any executed python script.  These functions are actually
>implemented in Java and provide some app-specific functionality to the
>python environment. 

I'm not one of the 'experts', but this is how I do it and it seems to work=
 fine; just 'execfile' the file with the functions:

 InputStream functionFileStream =3D FileIO.FindFileOrStream(=
 functionListName, dataPath, "functions", debugLevel);
 python.execfile( functionFileStream, functionListName); // pass the name=
 for parsing errors

This way the names are scoped into the top level.

(My 'FindFileOrStream' finds the function file in a file or jar in the=
 'dataPath'. I have a list of functions files in an XML configuration=
 file.)

- Jim

[Jython-users] embedding questions

[Seabloom, J. <jo...@ai...>]

Hello all,
	I'm working to embed jython within an in-house distributed java
application.  I'm really looking to solve two major problems and haven't
come to any answers from looking over the javadoc or the source code.

- I need a hook into the import functionality of the interpreter.  We store
scripts in JAR files that are 'hot-pluggable' into a running system, so when
interpreting a python script that imports another module, I would like to be
able to handle such an event so that I may look through these
'hot-pluggable' JAR files instead of relying on the sys.path or PYTHONPATH
variables. 

- I would also like to expose some python functions into the global
namespace of any executed python script.  These functions are actually
implemented in Java and provide some app-specific functionality to the
python environment.  The only way I've been able to accomplish this so far
is to write a Java class to implement the functions via methods, and then
insert the Java class as PyJavaInstance in the globals dictionary passed
into the PythonInterpreter constructor.  This has the side effect of
requiring syntax of the nature : 

	THE_APP.functionName()

Where 'THE_APP' is the name I used to register the object in the globals
dictionary.  Where I would prefer syntax like:

	functionName()

That is it.  I've solved these problems with Rhino and JavaScript, but the
javadoc provided with the rhino interpreter is much more complete than the
Jython javadoc.  Thank you to everyone ahead of time for you help.

Josh Seabloom
Applied Innovation

Re: [Jython-users] string.replace( java.lang.String )

[Oti <oh...@ya...>]

[ Samuele Pedroni ]

> From: Oti <oh...@ya...>
> > Hello,
> > 
> > I just stumbled over the following behaviour of string.replace().
> > Is it true I cannot pass a java.lang.String as first argument:
> > 
> > [appl|pwe] > jython
> > Jython 2.1 on java1.3.0 (JIT: null)
> > Type "copyright", "credits" or "license" for more information.
> > >>> import string
> > >>> from java.lang import String
> > >>> old = String( "old" )
> > >>> string.replace( old, "l", "d" )
> > Traceback (innermost last):
> >   File "<console>", line 1, in ?
> >   File "e:\jython21\Lib\string.py", line 409, in replace
> > TypeError: replace(): expected 2 args; got 3
> > >>> string.replace( old.intern(), "l", "d" )
> > 'odd'
> > 
> > 
> 
> Yes, the odd behavior is expected.
> 
> You should consider that string.py is coded
> assuming Python string input, and simply
> using the Python string object methods.
> 
> so string.replace(s,old,new,maxsplit)
> 
> simply calls s.replace(old,new,maxsplit)
> 
> now perchance Java strings have a replace method
> which takes only 2 arguments.
> 
> The other thing to consider 
> is that Java constructors
> called from Jython do not convert the result, its 
> Java instance nature is preserved.
> OTOH normal Java methods have their
> results always converted following the usual
> rules (eg. java.lang.String -> string):
> 
> >>> from java.lang import String
> >>> s=String("java")
> >>> s.__class__
> <jclass java.lang.String at 8070355>
> >>> type(s)
> <jclass org.python.core.PyJavaInstance at 6040101>
> >>> s2=s.toString()
> >>> type(s) == type('')
> 0
> >>> type(s2) == type('')
> 1
> 
> The following also fails:
> >>> s+'__'
> Traceback (innermost last):
>   File "<console>", line 1, in ?
> TypeError: __add__ nor __radd__ defined for these operands
> 
> I don't know if we should change all this.

No, I think you shouldn't.

Thank you very much for your explanation.
As you might havae guessed, I am (still) struggling to upgrade from
good old JPython1.0.3, where the example above ran.
I hope these are rare cases.

Best wishes,
Oti.

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Re: [Jython-users] RE: Issue with None and Serialization

[chuck c. <cc...@zi...>]

thanks brian...
on one front it was really simple...i tried import pickle and got an
ImportError and I moved on to writing my own serialization not even thinking
to try importing cPickle

i've switched to using the cPickle code now and everything works as expected

it looks like samuel has tracked down the bug...so all ends well

thanks
chuck

----- Original Message -----
From: "brian zimmer" <bz...@zi...>
To: <cc...@zi...>; <jyt...@li...>
Cc: <bu...@cu...>
Sent: Tuesday, March 12, 2002 7:50 PM
Subject: [Jython-users] RE: Issue with None and Serialization


> Chuck,
>
> Why can't you assume cPickle is available?  It's standard in the Jython
> dist as a Java-implemented module.  I have modified your example a bit
> to use it and it seems to behave properly.  Add the following two
> methods:
>
> --- code ---
>
> import cPickle
>
> def load_with_pickle(path):
> fp = open(path, "rb")
> try:
> data = cPickle.load(fp)
> finally:
> fp.close()
> return data
>
> def save_with_pickle(obj, path):
> fp = open(path, "wb")
> try:
> cPickle.dump(obj, fp)
> finally:
> fp.close()
>

Re: [Jython-users] Issue with None and Serialization

[Samuele P. <pe...@in...>]

From: chuck clark <cc...@zi...>
> I thought the problem might be that between serializing/deserializing I
> might somehow be getting a different instance of PyNone but this isn't
> the case as evidenced below when I inspect the objects in the
> interpreter after running th code above
> >>> type(a.attr)
> <jclass org.python.core.PyNone at 334527779>
> >>> type(b.attr)
> <jclass org.python.core.PyNone at 334527779>
> 

No, you're right it is a *bug* and your hypothesis is right,
only the above give you the "address" of the PyNone class.
The following is more revealing:
>>> execfile("test.py")
Testing initial object...
attr is None: 1
attr type is: org.python.core.PyNone
attr == None: 1
Testing deserialized object...
attr is None: 0
attr type is: org.python.core.PyNone
attr == None: 0
>>> id(None)
6503157
>>> id(a.attr)
6503157
>>> id(b.attr)
8302342

It is a problem with singletons serialization, it has gone
unnoticed until your report, it affects None, Ellipsis etc

Thanks, Samuele Pedroni.