Why isn't my codeblock executing and displaying the output?

Question

I have an org-mode file, with org-mode version 9+ (so my understanding is that Babel should be integrated). Then I have the following in the file

#+BEGIN_SRC python :exports both :results output
return 7 + 7
#+END_SRC

#+RESULTS:

I then compile to a PDF file. My understanding is that this should display both the codeblock and the evaluation of the codeblock. However the PDF just displays:

return 7 + 7

I have tried using print instead of return, but same outcome. What am I misunderstanding here?

Answer 1

Only if you use the header argument :results value the code of the block is wrapped by a function and the result of the code block is the return value of that function.

#+BEGIN_SRC python :exports both :results value
return 7 + 7
#+END_SRC

On the other hand :results output means that the code of the block is sent to the interpreter. The result of the code block is what the code prints to the standard output.

#+BEGIN_SRC python :exports both :results output
print "%d" % (7 + 7)
#+END_SRC

Answer 2

So I had misunderstood how the codeblocks were executed. You need an init.el file in ~/emacs.d/ and inside that I needed:

(org-babel-do-load-languages
 'org-babel-load-languages '((python . t)))

Once this was in place, when I convert the file to a PDF, it gives the option to execute the code.