Changing the Python source block to
#+BEGIN_SRC python :output results
def square (x):
return x*x
print(square(5))
#+END_SRC
didn't change anything here, neither with emacs24 nor with git emacs,
and I grepped (recursively) for ":output" in the directory where I
cloned
https://code.orgmode.org/bzg/org-mode.git and only found
references to ":output-dir" - except for a single occurrence of
":output" in contrib/lisp/ob-sclang.el...
Are you sure that you wrote it correctly?
Cheers, E. =)
http://angg.twu.net/#eev