Re: python :session issues

[Myles English <mylesenglish@gmail.com>]

Hi John,

John Kitchin writes:

> I have been trying to use the :session feature of babel for python code
> blocks. I have noticed a few things that might be areas for
> improvement. Some issues are related to what I think might be a need for
> sanitizing the code blocks and the output.
>
> I am using (insert (org-version)) 7.9.3a
> I am using python-mode 5.2 (more modern versions do not work with
> :session for me)
>
> The first small detail is illustrated here:
>
> #+BEGIN_SRC python :session
> a = 5
>
> b = 6
>
> print a + b
> #+END_SRC
>
> #+RESULTS:
> :
> : >>> >>> >>> 11
>
> In the output, there are three sets of >>>, due to the two empty
> lines. Compare this to
>
> #+BEGIN_SRC python :session
> a = 5
> b = 6
> print a + b
> #+END_SRC
>
> #+RESULTS:
> :
> : >>> 11
>
> I think it would be nice to sanitize the python code block sent to the
> interpreter to eliminate the empty lines, and avoid the multiple >>> in
> output. It would also be nice to have an option to not print those at
> all.
>
> The second issue is related. The following code does not work for me in
> :session, but it works fine as a standalone block. The issue is related
> to the presence of an empty line in the function definition. I like
> whitespace like this in functions sometimes for readability.
>
> #+BEGIN_SRC python :session
> def func(x):
>     'doc string'
>
>     return x**2
>
> print func(2)
> #+END_SRC
>
> #+RESULTS:
> :
> : ... >>>   File "<stdin>", line 1
> :     return x**2
> :     ^
> : IndentationError: unexpected indent
> : >>> None
>
> Removing the blank line works fine, but still has some non-pretty
> output.
>
> #+BEGIN_SRC python :session
> def func(x):
>     'doc string'
>     return x**2
>
> print func(2)
> #+END_SRC
>
> #+RESULTS:
> :
> : ... ... >>> 4
>
> One of the ellipsis is due to the doc string.
> #+BEGIN_SRC python :session
> def func(x):
>     return x**2
>
> print func(2)
> #+END_SRC
>
> #+RESULTS:
> :
> : ... >>> 4
>
> Interestingly, this did not work, because there is no empty line after
> the function definition. So, sanitizing could be tricky.
>
> #+BEGIN_SRC python :session
> def func(x):
>     'doc string'
>     return x**2
> print func(2)
> #+END_SRC
>
> #+RESULTS:
> :
> : ... ...   File "<stdin>", line 4
> :     print func(2)
> :         ^
> : SyntaxError: invalid syntax
>
> I think if there was a way to strip all the empty lines from the input,
> it would go a long way to making the output look like what I think most
> people would expect and want.
>
> Anyway, those are the examples I wanted to highlight in this
> post.
>
>
> 1. Do you see similar behavior, or is this a feature of my setup?

I haven't tried your examples (no time) but you would be able to tell if
it was a feature of your setup by making a minimum working example and
starting emacs with 'emacs -Q'.  If you see the thread in the footnote
it contains such an example.

> 2. Is there any interest in sanitizing the input and output of a
> python :session to get prettier output? if so, Any hints on where to
> start with that?

I had some problems recently with :session, there was a short discussion[1],
and last I heard the maintainer of python-mode.el is looking into it.

Myles

Footnotes: 
[1]  https://lists.gnu.org/archive/html/emacs-orgmode/2013-01/msg00888.html