Creating Packages

Last updated on 2025-09-30 | Edit this page

Overview

Questions

  • How to create a package?

Objectives

  • Learn setting up a project using modules
  • Learn common package structure
  • Learn to browse GitHub or juliahub for packages and find documentation

Melissa is now confident that her module is fine and she wants to make it available for the rest of her physics club. She decides to put it in a package. This way she can also locally use Julia’s package manager for managing her module.

From project to package

The path from having a module to having a package is actually very short: Packages need a name and a uuid field in their Project.toml.

A UUID is a universally unique identifier. Thankfully Julia comes with the UUIDs package, that can generate uuids for Melissa via UUIDs.uuid4().

In addition Melissa needs to have a specific directory structure. She looks at the example package Example.jl which has the following structure:

├── docs
│   ├── make.jl
│   ├── Project.toml
│   └── src
│       └── index.md
├── LICENSE.md
├── Project.toml
├── README.md
├── src
│   └── Example.jl
└── test
    └── runtests.jl
Callout

Make it a package

You can open your Project.toml and add name = <your name>, uuid = <your uuid> and optionally an authors field, each on a separate line.

The basic src structure can be generated with a complete Project.toml using the generate command from Pkg. Melissa enters pkg mode using ].

JULIA 

(@v1.11) pkg> generate projects/MelissasModule

OUTPUT 

  Generating  project MelissasModule:
    projects/MelissasModule/Project.toml
    projects/MelissasModule/src/MelissasModule.jl

Melissa’s new package directory structure looks like this.

├── Project.toml
└── src
    └── MelissasModule.jl

She opens the newly generated Project.toml to see the contents (The uuid and authors fields will be unique to you:

name = "MelissasModule"
uuid = "..."
authors = ["..."]
version = "0.1.0"

Melissa knows she needs the Trebuchet and ForwardDiff packages as dependencies. She activates her new project and adds them:

JULIA 

(@v1.11) pkg> activate projects/MelissasModule

OUTPUT 

  Activating project at `~/projects/MelissasModule`

JULIA 

(MelissasModule) pkg> add Trebuchet ForwardDiff

OUTPUT 

   Resolving package versions...
      Compat entries added for Trebuchet, ForwardDiff
    Updating `~/projects/MelissasModule/Project.toml`
  [f6369f11] + ForwardDiff v1.2.1
  [98b73d46] + Trebuchet v0.2.2
    Updating `~/projects/MelissasModule/Manifest.toml`
  [...]

The Project.toml now has entries for those dependencies:

name = "MelissasModule"
uuid = "..."
authors = ["..."]
version = "0.1.0"

[deps]
ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
Trebuchet = "98b73d46-197d-11e9-11eb-69a6ff759d3a"

[compat]
ForwardDiff = "1.2.1"
Trebuchet = "0.2.2"

The generated source file src/MelissasModule.jl looks like this:

JULIA 

module MelissasModule

greet() = print("Hello World!")

end # module MelissasModule

Melissa replaces the greet() function with the contents of her module she created earlier (except for the two lines using Pkg; there is no need to activate another project now that her module is part of a project with those dependencies).

Now Melissa can use

JULIA 

(@v1.11) pkg> dev . # or path to package instead of `.`

instead of needing to includet MelissasModule.jl, and she can write using MelissasModule instead of using .MelissasModule. She modifies MelissasCode.jl accordingly.

Register a package

In order for her friends to be able to get the package, Melissa registers the package in the general registry. This can be done either via JuliaHub or by making a pull request on GitHub which can also be automated by the Julia Registrator.

Creating a new package

Melissa thinks next time she will start with a package right away.

Browsing the packages she found PkgTemplates.jl and PkgSkeleton.jl which makes setting up the typical folder structure very easy.

Callout

Create your own package

Look at the documentation of the package creation helper packages and create a new package using generate.

Key Points
  • The general registry is hosted on GitHub.
  • Packaging is easy