Re: :tangle header argument not picked up in #+PROPERTY line or :PROPERTIES: block

[Joost Kremers <joostkremers@fastmail.fm>]

On Mon, Mar 30 2020, Ken Mankoff wrote:
> Header args overwrite. Change python to python+ to append header 
> args.

Are you sure? That's not documented anywhere I can find and it 
seems to be belied by the fact that if I put the headers in the 
order:

```
:PROPERTIES:
:header-args:python: :tangle out1.py
:header-args:python: :session py1 :results function
:END:
```

everything works as I would expect (the code blocks are tangled to 
a file `out1.py` *and* they are evaluated in a python session 
`py1`), meaning that *all* header args are picked up.

If I reverse the order and add a `+` sign, like so:

```
:PROPERTIES:
:header-args:python+: :session py1 :results function
:header-args:python+: :tangle out1.py
:END:
```

the code does indeed get tangled, but the `:results` header arg 
isn't picked up, because the code block doesn't produce any 
output.

For reference, this is my test file:

```
* Header 1
:PROPERTIES:
:header-args:python+: :session py1 :results function
:header-args:python+: :tangle out1.py
:END:

#+begin_src python
a=1
b=2
c=a+b
return c
#+end_src

#+RESULTS:
```


-- 
Joost Kremers
Life has its moments