Re: [O] noweb and :var statements

[Sebastian Miele]

Ken Mankoff <address@hidden> writes:

> Hi Sebastian,
>
> Thanks for your help. I was running with "-Q" but must have been
> making some other mistakes. It does work.
>
> As for your other email... I do know several tangles can go to the
> same file. And I may be using <<noweb>> incorrectly, but I'm using it
> for the following reasons:
>
> 1) I'd like to bury code that must run first but is inconsequential at
> the bottom of the Org file. Noweb lets me have a tangled <<setup>> at
> the top, and then hide the lengthy <<setup>> code elsewhere. Is this a
> correct use case?

Yes.

> 2) I'd like to import 10 tables, so I thought a noweb function might
> be useful for code reuse.
>
> I finally got the behavior I'm looking for. What I need to
> remember/understand is that <<noweb>> just pastes the body, and
> <<noweb()>> evaluates the function. From this, my Python code needs to
> generate Python code! I now have the following MWE that behaves as I
> want both for in-buffer C-c C-c eval of main code block and tangled
> results. The key bit of code is the last babel block.

A solution without having to write code-writing code is tangling to
different files (MWE3.py and setup.py). See the example below.

I read somewhere that Python has stong reflection features. It should be
possible to write Python code that, given a string and a value,
introduces a Python variable of that name and binds the value to it. If
you find out how that works, the mangle block below can be changed so
that the main block has e.g. setup.A.sum() instead of
setup.tables["A"].sum().

Final disclaimer: There may and probably are other possibilies that I do
not know or have not thought of.

* Main Project

#+NAME: main
#+BEGIN_SRC python :tangle MWE3.py :noweb yes :results output
import setup
print(setup.tables["A"].sum())
print(setup.tables["B"].sum())
#+END_SRC

* Data Tables
#+NAME: table_42
| foo |
|-----|
|  42 |
|  42 |

#+NAME: table_100
| bar |
|-----|
| 100 |

* Setup

#+BEGIN_SRC python :tangle setup.py
import numpy as np
tables={}
#+END_SRC

#+NAME: mangle
#+BEGIN_SRC python
tables[name] = np.array(table).astype(np.float).flatten()
#+END_SRC

#+BEGIN_SRC python :tangle setup.py :noweb yes :var table=table_42 :var name="A"
<<mangle>>
#+END_SRC

#+BEGIN_SRC python :tangle setup.py :noweb yes :var table=table_100 :var 
name="B"
<<mangle>>
#+END_SRC