I doubt it is Python specific, and I don't know why it would work in some places and not others. For me, the two character name does not work in elisp, but 1 or 3 does. I agree that seems buggy.

The origin of the problem is here:

#+BEGIN_SRC emacs-lisp
(list
 (string-match (org-babel-noweb-wrap) "<<A>>")
 (string-match (org-babel-noweb-wrap) "<<Ah>>")
 (string-match (org-babel-noweb-wrap) "<<Ahh>>"))
#+END_SRC

#+RESULTS:
| 0 | nil | 0 |

my regex fu is not adequate to identify the problem:

#+BEGIN_SRC emacs-lisp
(org-babel-noweb-wrap)
#+END_SRC

#+RESULTS:
: <<\([^
: ].+?[^ ]\|[^
: ]\)>>

That function is used in org-babel-expand-noweb-references. 


It is somewhat luck that I found that, I was tracing org-babel-expand-noweb-references to see where it was failing, and walked through that line to see it failed on "Ah", and worked on longer names.

John

-----------------------------------
Professor John Kitchin 
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803


On Mon, Feb 4, 2019 at 8:40 AM Emmanuel Charpentier <emm.charpentier@free.fr> wrote:
Le lundi 04 février 2019 à 08:11 -0500, John Kitchin a écrit :
The problem may be the name is only two characters long. Try Ahh instead. That works for me. 

Indeed. Nice catch ; how did you find this ?

Since this doesn't happen with emacs-lisp or Sage, and since nothing in the docs I've read so far suggests anything about the length of a block identifier, I consider this a bug in the Python language support code. What do you think ? Any hint ?

Thanks a lot !

--
Emmanuel Charpentier

John

-----------------------------------
Professor John Kitchin 
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803


On Mon, Feb 4, 2019 at 7:00 AM Emmanuel Charpentier <emm.charpentier@free.fr> wrote:
Seen in `org-mode' version `9.2'.

Using `noweb' syntax works OK with `emacs-lisp':

┌────
│ #+name: a
│ #+begin_src emacs-lisp
│   (setq L (append L (list i)))
│ #+end_src
│
│ #+name: b
│ #+begin_src emacs-lisp :noweb yes :exports both
│   ;; Lisp version
│   (setq L nil)
│   (dotimes (i 5) <<a>>)
│   L
│ #+end_src
└────

This gives :

┌────
│ (setq L (append L (list i)))
└────

┌────
│ ;; Lisp version
│ (setq L nil)
│ (dotimes (i 5) )
│ L
└────

The `noweb' syntax also works with `Sage' (a symbolic maths oriented
Python derivative):

┌────
│ #+name: Aaarghhh
│ #+begin_src sage
│   L.append(i)
│ #+end_src
│
│ #+name: Berde
│ #+begin_src sage :noweb yes :exports both
│   ## Python version
│   L=[]
│   for i in range(1,6):
│       <<Aaarghhh>>
│   L
│ #+end_src
└────

wich gives :

┌────
│ L.append(i)
└────

┌────
│ ## Sage version
│ L=[]
│ for i in range(1,6):
│
│ L
└────

But using the same syntax in Python fails miserably:

┌────
│ #+name: Ah
│ #+begin_src python
│   L.append(i)
│ #+end_src
│
│ #+name: Beee
│ #+begin_src python :noweb yes :exports both
│   ## Python version
│   L=[]
│   for i in range(1,6):
│       <<Ah>>
│   L
│ #+end_src
└────

┌────
│ L.append(i)
└────

┌────
│ ## Python version
│ L=[]
│ for i in range(1,6):
│     <<Ah>>
│ L
└────

┌────
│ []
└────


It *seems* that the "Ah" block is not expanded.

The code itself should be sound *if* it expanded:

┌────
│ #+name: B0
│ #+begin_src python :exports both
│   L=[]
│   for i in range(1,6):
│       L.append(i)
│   L
│ #+end_src
└────

┌────
│ L=[]
│ for i in range(1,6):
│     L.append(i)
│ L
└────

━━━━━━━━━━━━━━━
 1  2  3  4  5
━━━━━━━━━━━━━━━

During the compilation of the source of this mail, the following is
printed in the `*Python*' buffer:

┌────
│ >>> L.append(i)
│ >>>
│ >>> open('/tmp/babel-OJSsxf/python-dVESY4', 'w').write(str(_))
│ >>>
│ >>>
│ >>> 'org_babel_python_eoe'
│ 'org_babel_python_eoe'
│ >>> ## Python version
│ ... L=[]
│ >>> for i in range(1,6):
│ ...     <<Ah>>
│   File "<stdin>", line 2
│     <<Ah>>
│      ^
│ SyntaxError: invalid syntax
│ >>>
│ >>> L
│ []
│ >>>
│ >>> open('/tmp/babel-OJSsxf/python-9NR46u', 'w').write(str(_))
│ >>>
│ >>>
│ >>> 'org_babel_python_eoe'
│ 'org_babel_python_eoe'
│ >>> L=[]
│ >>> for i in range(1,6):
│ ...     L.append(i)
│ ...
│ >>> L
│ [1, 2, 3, 4, 5]
│ >>>
│ >>> open('/tmp/babel-OJSsxf/python-fW5gK0', 'w').write(str(_))
│ >>>
│ >>>
│ >>> 'org_babel_python_eoe'
│ 'org_babel_python_eoe'
│ >>>
└────

The source code of this mail is attached.

--
Emmanuel Charpentier