What is output for org-babel?

What is output for org-babel?

[andrea Crotti]

I'm with org-mode 6.31a, I was trying to
get output in the exported files but I never see the output.

So I investigate and for example this

#+BEGIN_SRC python
import os; os.listdir(os.getcwd())
#+END_SRC

doesn't return any output while this

#+BEGIN_SRC python
"hello"
#+END_SRC

does and this:

#+BEGIN_SRC python
return "hello"
#+END_SRC
Again doesn't.

I guess that the returned value is depending also on the language,
but in general what's the rule?

Another little thing, I have a file with many haskell source blocks.
They are separated because they are different answers,
but if they are loaded separately they don't work.
So is there a way to take all the source code and load it at once?

Something like more or less:
(append-to-buffer "haskell-buf" (get-code "exercises.org"))

Re: What is output for org-babel?

[Darlan Cavalcante Moreira]

COmments are inline.

At Thu, 5 Nov 2009 11:17:39 +0000 (UTC),
andrea Crotti <andrea.crotti.0@gmail.com> wrote:
> 
> I'm with org-mode 6.31a, I was trying to
> get output in the exported files but I never see the output.
> 
> So I investigate and for example this
> 
> #+BEGIN_SRC python
> import os; os.listdir(os.getcwd())
> #+END_SRC

This does not return anything for me either, but
#+BEGIN_SRC python
import os
os.listdir(os.getcwd())
#+END_SRC
works as expected. This is strange, since "import os; os.listdir(os.getcwd())"
is valid and will work if typed in the python interpreter directly.

> 
> doesn't return any output while this
> 
> #+BEGIN_SRC python
> "hello"
> #+END_SRC
> 
> does and this:
> 
> #+BEGIN_SRC python
> return "hello"
> #+END_SRC
> Again doesn't.

I don't think this is suppose to work. As I understand org-babel send this code
to python without any processing but you are not inside a python
function. Therefore this is as if you have typed 'return "hello"' in the
interpreter and it will result in an error. That's why no output is shown.
Change "#+BEGIN_SRC python" to "#+BEGIN_SRC python :results output" and you will
see the error.

However, if the code is sent to the python interpreter as it is, then it bugs me
why "import os; os.listdir(os.getcwd())" didn't work.

- Darlan

> I guess that the returned value is depending also on the language,
> but in general what's the rule?
> 
> Another little thing, I have a file with many haskell source blocks.
> They are separated because they are different answers,
> but if they are loaded separately they don't work.
> So is there a way to take all the source code and load it at once?
> 
> Something like more or less:
> (append-to-buffer "haskell-buf" (get-code "exercises.org"))
> 
> 
> 
> _______________________________________________
> Emacs-orgmode mailing list
> Remember: use `Reply All' to send replies to the list.
> Emacs-orgmode@gnu.org
> http://lists.gnu.org/mailman/listinfo/emacs-orgmode

Re: What is output for org-babel?

[andrea Crotti]

Darlan Cavalcante Moreira <darcamo <at> gmail.com> writes:

> 
> However, if the code is sent to the python interpreter as it is, then it
> bugs me
> why "import os; os.listdir(os.getcwd())" didn't work.

I tried to look at the code of org-babel-python
but it's a bit too complicated to understand how my body
is manipulated...

For the second question I made, it would be even
better to have a mechanism that allows to insert
logical parts of another buffer in my org-mode file.

Something like

#+INCLUDE file.hs::fun_def

Where fun_def is the definition of a function.
programming modes know how to split this kind of things, so
also org-mode could now, right?

Re: Re: What is output for org-babel?

[Carsten Dominik]

Dear all,

please remember to put

     [babel]

into the subject line of messages that discuss features of org-babel.
I would like to keep these messages on the list as well, but we
should make filtering easy for people who are not interested
in these discussions.

- Carsten

On Nov 6, 2009, at 1:13 PM, andrea Crotti wrote:

> Darlan Cavalcante Moreira <darcamo <at> gmail.com> writes:
>
>>
>> However, if the code is sent to the python interpreter as it is,  
>> then it
>> bugs me
>> why "import os; os.listdir(os.getcwd())" didn't work.
>
> I tried to look at the code of org-babel-python
> but it's a bit too complicated to understand how my body
> is manipulated...
>
> For the second question I made, it would be even
> better to have a mechanism that allows to insert
> logical parts of another buffer in my org-mode file.
>
> Something like
>
> #+INCLUDE file.hs::fun_def
>
> Where fun_def is the definition of a function.
> programming modes know how to split this kind of things, so
> also org-mode could now, right?
>
>
>
> _______________________________________________
> Emacs-orgmode mailing list
> Remember: use `Reply All' to send replies to the list.
> Emacs-orgmode@gnu.org
> http://lists.gnu.org/mailman/listinfo/emacs-orgmode

- Carsten

Re:[babel] Re: What is output for org-babel?

[Thomas S. Dye]

On Nov 6, 2009, at 2:13 AM, andrea Crotti wrote:

> Darlan Cavalcante Moreira <darcamo <at> gmail.com> writes:
>
>>
>> However, if the code is sent to the python interpreter as it is,  
>> then it
>> bugs me
>> why "import os; os.listdir(os.getcwd())" didn't work.
>
> I tried to look at the code of org-babel-python
> but it's a bit too complicated to understand how my body
> is manipulated...
>
> For the second question I made, it would be even
> better to have a mechanism that allows to insert
> logical parts of another buffer in my org-mode file.
>
> Something like
>
> #+INCLUDE file.hs::fun_def
>
> Where fun_def is the definition of a function.
> programming modes know how to split this kind of things, so
> also org-mode could now, right?
>
>
>
> _______________________________________________
> Emacs-orgmode mailing list
> Remember: use `Reply All' to send replies to the list.
> Emacs-orgmode@gnu.org
> http://lists.gnu.org/mailman/listinfo/emacs-orgmode

Hi Andrea,

If I understand your question correctly, there might be several ways  
to achieve this with existing org-babel functions.  Here are two that  
might work.

1) Establish a :session and make fun_def available there, or
2) Explore the possibilities offered by Library of Babel.  This is  
something I haven't explored yet, but it appears to be designed for  
the problem you're describing.

HTH,
Tom

Re: What is output for org-babel?

["Martin G. Skjæveland"]

andrea Crotti wrote:
> I'm with org-mode 6.31a, I was trying to
> get output in the exported files but I never see the output.

Hi,

not sure if this is related -- or helpful, but here goes!

When I export the following file:

----------------start---------------
* lowercase
#+begin_src python :exports results
2+2
#+end_src

* uppercase
#+BEGIN_SRC python :exports results
2+2
#+end_src
----------------end---------------

the results are (copied from pdf):

----------------start---------------
1   lowercase
  4

2   uppercase
2+2
----------------end---------------

Writing "begin_src" in lowercase or uppercase makes a difference. I am 
not sure if this is a feature or a bug.

Martin

Re: What is output for org-babel?

["Martin G. Skjæveland"]

Martin G. Skjæveland wrote:
> andrea Crotti wrote:
>> I'm with org-mode 6.31a, I was trying to
>> get output in the exported files but I never see the output.
>
> Writing "begin_src" in lowercase or uppercase makes a difference. I am 
> not sure if this is a feature or a bug.

Oh, forgot to mention: I can't make any of the snippets you sent work. 
Everything in the source blocks is exported as verbatim text, regardless 
of upper/lowercase, or :results output or not.

Martin

Re: What is output for org-babel?

[Dan Davison]

"Martin G. Skjæveland" <martige@ifi.uio.no> writes:

> andrea Crotti wrote:
>> I'm with org-mode 6.31a, I was trying to
>> get output in the exported files but I never see the output.
>
> Hi,
>
> not sure if this is related -- or helpful, but here goes!
>
> When I export the following file:
>
> ----------------start---------------
> * lowercase
> #+begin_src python :exports results
> 2+2
> #+end_src
>
> * uppercase
> #+BEGIN_SRC python :exports results
> 2+2
> #+end_src
> ----------------end---------------
>
> the results are (copied from pdf):
>
> ----------------start---------------
> 1   lowercase
>  4
>
> 2   uppercase
> 2+2
> ----------------end---------------
>
> Writing "begin_src" in lowercase or uppercase makes a difference. I am
> not sure if this is a feature or a bug.

Bug. However I'm not sure whether it is in org-mode or org-babel. In
general in org-mode, begin_src and BEGIN_SRC are equivalent (true for
all #+XXX directives I think). However, in this case the org-exp-blocks
client (org-babel) associates 'src' with its own block exporter, but it
says nothing about 'SRC'. So the solution could either be:

(a) Bug in the org-exp-blocks client (org-babel). The client should
explicitly hook up 'SRC' to its block pre-processor.

(b) Bug in org-mode. Org-exp-blocks should call the block pre-processor
for 'src' when it finds 'SRC' (and equivalently, if a client registers
'SRC', then 'src' should trigger it.)

I'm leaning towards (b), seeing as we already have the case
insensitivity in org-mode.

Dan


>
> Martin
>
>
> _______________________________________________
> Emacs-orgmode mailing list
> Remember: use `Reply All' to send replies to the list.
> Emacs-orgmode@gnu.org
> http://lists.gnu.org/mailman/listinfo/emacs-orgmode

Re: What is output for org-babel?

[Dan Davison]

Darlan Cavalcante Moreira <darcamo@gmail.com> writes:

> COmments are inline.
>
> At Thu, 5 Nov 2009 11:17:39 +0000 (UTC),
> andrea Crotti <andrea.crotti.0@gmail.com> wrote:
>> 
>> I'm with org-mode 6.31a, I was trying to
>> get output in the exported files but I never see the output.
>> 
>> So I investigate and for example this
>> 
>> #+BEGIN_SRC python
>> import os; os.listdir(os.getcwd())
>> #+END_SRC
>
> This does not return anything for me either, but
> #+BEGIN_SRC python
> import os
> os.listdir(os.getcwd())
> #+END_SRC
> works as expected. This is strange, since "import os; os.listdir(os.getcwd())"
> is valid and will work if typed in the python interpreter directly.

This is a limitation of the current implementation of :results value
evaluation. For now, while we work out a good solution, semi-colon
separated statements on the same line (as well as multiline
continuations) should be avoided when using :results value (the
default). It does work with :results output:

#+BEGIN_SRC python :results output
import os; print os.listdir(os.getcwd())
#+END_SRC

Thanks for pointing this problem out.

Dan

Re: What is output for org-babel?

[Dan Davison]

Dan Davison <davison@stats.ox.ac.uk> writes:

> Darlan Cavalcante Moreira <darcamo@gmail.com> writes:
>
<...>
>>> So I investigate and for example this
>>> 
>>> #+BEGIN_SRC python
>>> import os; os.listdir(os.getcwd())
>>> #+END_SRC
>>
>> This does not return anything for me either, but
>> #+BEGIN_SRC python
>> import os
>> os.listdir(os.getcwd())
>> #+END_SRC
>> works as expected. This is strange, since "import os; os.listdir(os.getcwd())"
>> is valid and will work if typed in the python interpreter directly.
>
> This is a limitation of the current implementation of :results value
> evaluation. 

I've just pushed a change which fixes this and related problems. It
introduces a change for python users: when using the default evaluation
mode (':results value' non-session), if you want the source code block
to return a value, you must now include the 'return' statement that
would be required if you were writing a python function definition.

On Worg I've added some more detailed documentation of exactly how the
result is obtained in the four different cases (value/output,
session/non-session), and I'm also pasting that below.

Dan


*** Evaluation results: output/value & session/non-session
    
    The following applies particularly to perl, python, R and ruby.

Nature of Results:

|        | non-session              | session                             |
|--------+--------------------------+-------------------------------------|
| value  | value of last expression | value of last expression            |
| output | contents of stdout       | concatenation of interpreter output |


Note that in ':results value' (session and non-session), the result is
imported into org-mode as a table (a one- or two-dimensional vector of
strings or numbers) when appropriate.

**** :results value (non-session)
     This is the default. Internally, the value is obtained by
     wrapping the code in a function definition in the external
     language, and evaluating that function. Therefore, code should be
     written as if it were the body of such a function. In particular,
     note that python does not automatically return a value from a
     function unless a =return= statement is present, and so a
     'return' statement will usually be required in python :results
     value (non-session).

     This is the only one of the four evaluation contexts in which the
     code is automatically wrapped in a function definition.

**** :results output (non-session)
     The code is passed to the interpreter as an external process, and
     the contents of the standard output stream is returned as text. (In
     certain languages this also contains the error output stream; this
     is an area for future work.)

**** :results value (session)
     The code is passed to the interpreter running as an interactive
     emacs inferior process. The result returned is the result of the
     last evaluation performed by the interpreter. (This is obtained in
     a language-specific manner: the value of the variable =_= in
     python and ruby, and the value of =.Last.value= in R).

**** :results output (session)
     The code is passed to the interpreter running as an interactive
     emacs inferior process. The result returned is the concatenation
     of the sequence of (text) output from the interactive
     interpreter. Notice that this is not necessarily the same as what
     would be sent to stdout if the same code were passed to a
     non-interactive interpreter running as an external process. For
     example, compare the following two blocks:

#+begin_src python :results output
  print "hello"
  2
  print "bye"
#+end_src

#+resname:
: hello
: bye

In non-session mode, the '2' is not printed and does not appear.

#+begin_src python :results output :session
  print "hello"
  2
  print "bye"
#+end_src

#+resname:
: hello
: 2
: bye

But in session mode, the interactive interpreter receives input '2'
and prints out its value, '2'. (Indeed, the other print statements are
unnecessary here).