Steven G. Johnson

Installing Conda.jl does not actually install the distro — that only happens when a user, or a package like PyCall, first requests that something be installed. e.g. try: ```jl import...

PyCall just searches the `$PATH` environment variable for `python3`. If nix-shell uses some other mechanism for `which`, that won't work. The workaround is simply to set ```jl ENV["PYTHON"]="/nix/store/rppr9s436950i1dlzknbmz40m2xqqnxc-python3-3.9.9/bin/python3" Pkg.build("PyCall") ```...

What is the output of `Pkg.build("PyCall")`?

Weird. There is no other output from `using PyCall`?

Okay, I can reproduce the problem after doing a `Pkg.update()`.

`Pkg.pin("MacroTools", v"0.3.4")` works around the problem for me.

Sounds good; I've been hoping for Pkg support for build preferences for a long time.

I would definitely like to switch PyCall to use the new Preferences architecture via https://github.com/JuliaPackaging/Preferences.jl … it doesn't seem like it needs a separate package anymore, so this PR should...

It doesn't require the internet. You can build PyCall to use a local, pre-installed Python distribution by setting the `PYTHON` environment variable. Moreover, this is about building — i.e. installing...

I see. Yes, it seems straightforward to check whether `conda list` includes `numpy` before adding.