Using ty with the helix editor

The folks at Astral have released ty, which they define as:

An extremely fast Python type checker and language server, written in Rust.

You can read more in the blog post announcing it.

Today, I set it up with helix. To make it work, we first have to install it. Using uv, it’s as easy as typing:

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uv tool install ty@latest

Then, edit your ~/.config/helix/languages.toml and add the following:

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[language-server.ty]
command = "ty"
args = ["server"]

[[language]]
name = "python"
scope = "source.python"
injection-regex = "python"
file-types = ["py","pyi","py3","pyw",".pythonstartup",".pythonrc"]
shebangs = ["python"]
roots = [".", "pyproject.toml"]
comment-token = "#"
language-servers = ["ty"]
indent = { tab-width = 4, unit = "    " }
auto-format = true

At this point, you can start using it, but there are a few handy things to know:

• By default, ty will search for first-party modules in the project’s root directory or the src directory, if present.
• If they are located elsewhere, you need to update your pyproject.toml like so:

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[tool.ty.environment]
root = ["./app"]

• Third-party modules are searched for within a virtual environment, determined by:
  1. An environment variable called VIRTUAL_ENV.
  2. A .venv directory in the project root or working directory.
  3. The --python or --venv flag when invoking it.
  4. A configuration in pyproject.toml:

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[tool.ty.environment]
python = "./custom-venv-location/.venv"

That’s it. Now, when editing files with hx, you should get all of ty’s goodness!