jython-users

[Jython-users] OSError: [Errno 0] chdir not supported in Java?

[Dinu G. <gh...@da...>]

Hi, 

I'm just starting to use Jython on OS X and run into several
problems, obne of them being this:

[localhost:~] dinu% jython
Jython 2.1 on java1.3.1 (JIT: null)
Type "copyright", "credits" or "license" for more information.
>>> import os
>>> os.chdir('..')
Traceback (innermost last):
  File "<console>", line 1, in ?
  File "/Applications/Additions/Jython-2.1/Lib/javaos.py", line 56, in chdir
OSError: [Errno 0] chdir not supported in Java: ..
>>> 

Any ideas? 

Thanks,

Dinu

Re: [Jython-users] OSError: [Errno 0] chdir not supported in Java?

[Samuele P. <ped...@bl...>]

No this one is not a bug, 
chdir is not supported by Jython.
Because it is not supported by Java.
We could workaround
but there is no clear win in that.

It should be noted that while Jython is
an implementation of Python and
it is a goal that portable code 
between Python and Jython
(www.anygui.org is example) can be
written,

it is not a goal that Python code
written without thinking about Jython
can be always ported, especially
for shell-programming-like programs.

Jython is Python for Java as a platform
and tries to follow the platform philosophy
without workarounding too much.

So there are tasks for which Python
is good and Jython not so much,
changing this is a low priority thingy.

regards, Samuele Pedroni.

----- Original Message ----- 
From: Dinu Gherman <gh...@da...>
To: <jyt...@li...>
Sent: Monday, February 25, 2002 6:22 PM
Subject: [Jython-users] OSError: [Errno 0] chdir not supported in Java?


> Hi, 
> 
> I'm just starting to use Jython on OS X and run into several
> problems, obne of them being this:
> 
> [localhost:~] dinu% jython
> Jython 2.1 on java1.3.1 (JIT: null)
> Type "copyright", "credits" or "license" for more information.
> >>> import os
> >>> os.chdir('..')
> Traceback (innermost last):
>   File "<console>", line 1, in ?
>   File "/Applications/Additions/Jython-2.1/Lib/javaos.py", line 56, in chdir
> OSError: [Errno 0] chdir not supported in Java: ..
> >>> 
> 
> Any ideas? 
> 
> Thanks,
> 
> Dinu
> 
> 
> _______________________________________________
> Jython-users mailing list
> Jyt...@li...
> https://lists.sourceforge.net/lists/listinfo/jython-users
> 

Re: [Jython-users] OSError: [Errno 0] chdir not supported in Java?

[Dinu G. <gh...@da...>]

Samuele Pedroni <ped...@bl...>:

> No this one is not a bug, 
> chdir is not supported by Jython.
> Because it is not supported by Java.
> We could workaround
> but there is no clear win in that.
> 
> It should be noted that while Jython is
> an implementation of Python and
> it is a goal that portable code 
> between Python and Jython
> (www.anygui.org is example) can be
> written,
> 
> it is not a goal that Python code
> written without thinking about Jython
> can be always ported, especially
> for shell-programming-like programs.
> 
> Jython is Python for Java as a platform
> and tries to follow the platform philosophy
> without workarounding too much.
> 
> So there are tasks for which Python
> is good and Jython not so much,
> changing this is a low priority thingy.
> 
> regards, Samuele Pedroni.


Ciao Samuele,

I see this has been asked before already on this list.
Sorry for not checking earlier! But I also see that it
is not impossible to implement chdir and friends in 
Java despite its security concerns as the following 
should make clear:

  http://www.hio.hen.nl/java/nl/nl/hen/ict/unix/Unix.html

Needless to say, I'd opt for Jython being more similar
to Python instead of Java, if for no other reason than 
the higher similarity of the "Jython" string to "Python"
than to "Java"! ;-)

Seriously, if it's possible to use chdir-like stuff why
not add it and make both happy, Java people missing it
*and* Python folks reusing their scripts...? Maybe some
Java guys will be more inclined to being dragged over
to Python?

Dinu

Re: [Jython-users] OSError: [Errno 0] chdir not supported in Java?

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

Have you seen that it requires 
a JNI lib?

Samuele Pedroni.

----- Original Message ----- 
From: Dinu Gherman <gh...@da...>
To: Samuele Pedroni <pe...@in...>
Cc: <jyt...@so...>
Sent: Tuesday, February 26, 2002 9:01 AM
Subject: Re: [Jython-users] OSError: [Errno 0] chdir not supported in Java?


> Samuele Pedroni <ped...@bl...>:
> 
> > No this one is not a bug, 
> > chdir is not supported by Jython.
> > Because it is not supported by Java.
> > We could workaround
> > but there is no clear win in that.
> > 
> > It should be noted that while Jython is
> > an implementation of Python and
> > it is a goal that portable code 
> > between Python and Jython
> > (www.anygui.org is example) can be
> > written,
> > 
> > it is not a goal that Python code
> > written without thinking about Jython
> > can be always ported, especially
> > for shell-programming-like programs.
> > 
> > Jython is Python for Java as a platform
> > and tries to follow the platform philosophy
> > without workarounding too much.
> > 
> > So there are tasks for which Python
> > is good and Jython not so much,
> > changing this is a low priority thingy.
> > 
> > regards, Samuele Pedroni.
> 
> 
> Ciao Samuele,
> 
> I see this has been asked before already on this list.
> Sorry for not checking earlier! But I also see that it
> is not impossible to implement chdir and friends in 
> Java despite its security concerns as the following 
> should make clear:
> 
>   http://www.hio.hen.nl/java/nl/nl/hen/ict/unix/Unix.html
> 
> Needless to say, I'd opt for Jython being more similar
> to Python instead of Java, if for no other reason than 
> the higher similarity of the "Jython" string to "Python"
> than to "Java"! ;-)
> 
> Seriously, if it's possible to use chdir-like stuff why
> not add it and make both happy, Java people missing it
> *and* Python folks reusing their scripts...? Maybe some
> Java guys will be more inclined to being dragged over
> to Python?
> 
> Dinu
> 
> 

Re: [Jython-users] OSError: [Errno 0] chdir not supported in Java?

[<bc...@wo...>]

[Dinu Gherman]

>Hi, 
>
>I'm just starting to use Jython on OS X and run into several
>problems, obne of them being this:
>
>[localhost:~] dinu% jython
>Jython 2.1 on java1.3.1 (JIT: null)
>Type "copyright", "credits" or "license" for more information.
>>>> import os
>>>> os.chdir('..')
>Traceback (innermost last):
>  File "<console>", line 1, in ?
>  File "/Applications/Additions/Jython-2.1/Lib/javaos.py", line 56, in chdir
>OSError: [Errno 0] chdir not supported in Java: ..
>>>> 
>
>Any ideas? 

As Samuele has explained, we can't do a chdir in 100% java and we will
*never* include JNI code with the jython distribution.

But we could (as we already do for the readline module) include support
code that require the presence of a JNI module to work. So if anybody
needed chdir() or chmod() or the full stat() values badly enough, she
could create a copy of the javaos.py module that used one of the JNI
module (there are several such candidates). 

We could then add a mechanisme to jython (in the registry) that allowed
users to choose either the existing 100% pure java version of "os" or
one the JNI alternatives.

The fact that I haven't maintained jnios for quite a while should be a
good indication that I don't need chdir() myself.

regards,
finn

Re: [Jython-users] OSError: [Errno 0] chdir not supported in Java?

[Dinu G. <gh...@da...>]

Finn Bock <bc...@wo...>:

> As Samuele has explained, we can't do a chdir in 100% java and we will
> *never* include JNI code with the jython distribution.

Thanks for the clarification! I got the same explanation from Samuele 
over private email. Thanks, Samuele!

> But we could (as we already do for the readline module) include support
> code that require the presence of a JNI module to work. So if anybody
> needed chdir() or chmod() or the full stat() values badly enough, she
> could create a copy of the javaos.py module that used one of the JNI
> module (there are several such candidates). 
> 
> We could then add a mechanisme to jython (in the registry) that allowed
> users to choose either the existing 100% pure java version of "os" or
> one the JNI alternatives.
>
> The fact that I haven't maintained jnios for quite a while should be a
> good indication that I don't need chdir() myself.

I'll check soon if I really need chdir or if I can replace it 
somehow... In fact, what I'm trying to do is port the ReportLab
toolkit to Jython, and chdir is what seems to prevent the test
suite (and some tools and demos) from working.

So, my frustration is maybe more with Java than with Jython and
surely I should have better investigated the issues instead of 
showing my Java ignorance. Sorry for that!

What I'd suggest is some sort of collection of "porting stories"
(Python to Jython) and/or issues to expect when doing this kind
of thing. I'm not sure the FAQ is the best place for that, but
maybe I'm wrong. OTOH, maybe it is too much to ask from Python
programmers to code in a Jython-friendly way? Well, at least it
would be helpful to know where to expect potential pitfalls.
What do people think?

The good news is that many parts of ReportLab seem to be working
ok, especially the vector graphics stuff (after fixing the list
builtin function)! 

Regards,

Dinu

Re: [Jython-users] OSError: [Errno 0] chdir not supported in Java?

[Mats W. <ma...@la...>]

 >What I'd suggest is some sort of collection of "porting stories"
 >(Python to Jython) and/or issues to expect when doing this kind
 >of thing. I'm not sure the FAQ is the best place for that, but
 >maybe I'm wrong.

I think a "porting FAQ", whether integrated with the main
FAQ or not, is always a good idea.  It provides a way to
capture particular issues that maybe don't belong in the
main docs, but still can save folks some time if documented
somewhhere.