Creating a Julia Package
Project Environment
If you want to create a simple script that depends on external libraries, you should create a "project environment". This means making a Project.toml file like the one below.
[deps]
"<Installed Package 1>" = "<UUID for Installed Package 1>"
"<Installed Package 2>" = "<UUID for Installed Package 2>"
"<Installed Package 3>" = "<UUID for Installed Package 3>"
To install an external library (for example, TargetPackage), run the following in your terminal:
julia --project -e 'using Pkg; Pkg.add("TargetPackage")'
Package Directory
If you want to create a reusable package or a larger scale script, you should create a "package directory".
Choosing the layout
Default: in-place layout. Create ./Project.toml and ./src/MyPkg.jl directly in the current working directory, with no subdirectory named after the package. Use this whenever the user asks to "create a package MyPkg" without further qualification.
Opt-in: subdirectory layout. Only use this when the user explicitly asks for a subdirectory — for example "create the package under a new directory", "サブディレクトリを作って", "MyPkg/ 配下に作って", or when the user is bootstrapping multiple packages side by side under a single workspace and a subdirectory is necessary to disambiguate them.
Do NOT use Pkg.generate("MyPkg") for the in-place layout — it always creates a subdirectory. The in-place layout is the default and must be produced by hand-writing the files (see the steps below).
In-place layout (default, no subdirectory)
To create Project.toml and src/MyPkg.jl directly in the current working directory:
-
Generate a UUID for the uuid field of Project.toml:
$ julia -E 'using UUIDs; string(uuid4())'
"43d6671a-6eab-408d-9ef9-8f584d9146fb" # Example output.
-
Write ./Project.toml with the package name and the UUID from step 1:
name = "MyPkg"
uuid = "43d6671a-6eab-408d-9ef9-8f584d9146fb"
authors = ["Your Name <you@example.com>"]
version = "0.1.0"
-
Write ./src/MyPkg.jl with the module skeleton:
module MyPkg
greet() = "Hello"
end # module MyPkg
-
Verify by loading the package from the current directory:
$ julia --project=. -e 'using MyPkg; println(MyPkg.greet())'
Subdirectory layout (opt-in only)
Only use this when the user explicitly asks for it. To create a package named MyPkg under a new subdirectory, run:
$ julia -e 'using Pkg; Pkg.generate("MyPkg")'
This will create:
$ tree
.
└── MyPkg
├── Project.toml
└── src
└── MyPkg.jl
3 directories, 2 files