Question: I have a problem with using packages in Julia. It has worked before, and I'm not really sure why this has changed or how to troubleshoot. 

I have a folder 
`/my_path/julia/packages`
with Julia packages. For example, there is a folder
`/my_path/julia/packages/FFTW/`
with the FFTW package. 
Further, I have changed the depot path to point at this directory by assigning `JULIA_DEPOT_PATH` before starting julia, so that

`Base.DEPOT_PATH = ["/my_path/julia/"]`

However, if I run
`julia> using FFTW`
I get the following error message:

> 
> ERROR: ArgumentError: Package FFTW not found in current path:
>  - Run `import Pkg; Pkg.add("FFTW")` to install the FFTW package.
> 
> 
> 

Any idea how I can troubleshoot or fix this?

Answer: 
Unless you have a specific reason to do so (and if this is the case I'd be interested to hear it!), you don't need to fiddle with the `DEPOT_PATH` or `LOAD_PATH` variables: using Julia's [package manager](https://docs.julialang.org/en/v1/stdlib/Pkg/#Pkg-1) should be enough to cover your needs most of the time.

In this specific instance, have you tried to do what the error message suggests?

```
julia> import Pkg
julia> Pkg.add("FFTW")

```
[`LOAD_PATH`](https://docs.julialang.org/en/v1/base/constants/#Base.LOAD_PATH), not `DEPOT_PATH`, will modify code loading.

You want to do something like `push!(LOAD_PATH, /my_path/julia/packages)`.

I will echo @ffevotte and strongly suggest to not modify `LOAD_PATH` unless necessary. The benefits of organizing dependencies into Pkg environments far outweigh the small overhead of declaring them explicitly through `Pkg.add`.