Take environment variables directly from the _environment file

[albertomercurio]

Following this page on the official documentation of Quarto, it is possible to define environment variables directly inside the _environment file. This is very useful when we need to define many variables used on many files.

Apparently, the only way that works so far is by writing the following yaml in each file

engine: julia
julia:
    env: ["JULIA_NUM_THREADS=16", "JULIA_CONDAPKG_BACKEND=Null", "JULIA_PYTHONCALL_EXE=../pyenv/bin/python"]

[MichaelHatherly]

With the following file structure I was able to retrieve envvars that were set in an _environment file:

/
  _environment
  _quarto.yml
  file.qmd

_environment:

FOO=bar

file.qmd:

---
engine: julia
---

```{julia}
ENV["FOO"]
```

_quarto.yml:

which did give the correct output:

@albertomercurio with the above MWE are you also able to see the same output, or does that also fail for you?

---

What does not work for me, is changing the value of an envvar set in that file while the julia process that runs the server is active, since it appears to me that those environment variables are defined when that process starts up. When they are later changed and a new render is requested they can't be reset. Quarto does not pass them as data to the server process from what I can tell, otherwise we could intercept them and define them correctly.

Perhaps this is the same behaviour as other engines.

[albertomercurio]

Oh, yes. I was using export VARIABLE=something, but it should be without export.

I think we can close this issue. But, I have just one related question. I have now the following environment variables needed for PythonCall.jl

JULIA_NUM_THREADS=16
JULIA_CONDAPKG_BACKEND=Null
JULIA_PYTHONCALL_EXE=pyenv/bin/python

but the python path is relative to the _environment file location. This means that if I have a .qmd file in a subfolder, this will fail. Is there a way to define the python variable without explicitly write the absolute path of the python executable?

[MichaelHatherly]

I have now the following environment variables needed for PythonCall.jl

Does setting those just in the first cell of your notebook that needs then, via ENV["JULIA_PYTHONCALL_EXE"] = ..., work for you? Picking the value of the path dynamically based on the location of the notebook.

[albertomercurio]

I'm currently using the following yaml configuration on each .qmd file

julia:
    env: ["JULIA_NUM_THREADS=16", "JULIA_CONDAPKG_BACKEND=Null", "JULIA_PYTHONCALL_EXE=../pyenv/bin/python"]

since they are simply in the next subfolder. I was searching for something global.

I tried to write something dynamics in the _environment file, like

JULIA_PYTHONCALL_EXE=$(which python)

to automatically take the python path. but this doesn't work.

[MichaelHatherly]

In a ```{julia} cell though? Not in the julia.env frontmatter key:

```{julia}
ENV["JULIA_PYTHONCALL_EXE"] = ...
```

```{julia}
using PythonCall
```

I'd assume something like that would be fine, PythonCall is only loaded after the env var is set. It's not like setting threading for julia via an env var where it has to happen prior to start up.

[albertomercurio]

Ok thanks