By name: ty-skills description: > Python type checking expertise using ty - the extremely fast type checker by Astral. Use when: (1) Adding type annotations to Python code, (2) Fixing type errors reported by ty, (3) Migrating from mypy/pyright to ty, (4) Configuring ty for projects, (5) Understanding advanced type patterns (generics, protocols, intersection types), (6) Setting up ty in editors (VS Code, Cursor, Neovim, PyCharm).
ty-skills
Master Python type checking with ty - the extremely fast type checker written in Rust by Astral (creators of uv and Ruff).
When to Use This Skill
- Adding type annotations to Python code
- Fixing type errors and diagnostics from ty
- Configuring ty rules and severity levels
- Migrating from mypy or pyright to ty
- Understanding advanced type patterns (intersection types, protocols, generics)
- Setting up ty language server in your editor
Quick Start
# Install
uv tool install ty
# or: pip install ty
# Check current directory
ty check
# Check specific files
ty check src/
# Full diagnostics
ty check --output-format full
Configuration
Configure via pyproject.toml:
[tool.ty.environment]
python-version = "3.12"
python = "./.venv"
python-platform = "linux"
root = ["./src"]
extra-paths = ["./typings"]
[tool.ty.rules]
# error: fail CI, warn: report, ignore: disable
possibly-unresolved-reference = "error"
invalid-argument-type = "error"
division-by-zero = "warn"
unused-ignore-comment = "warn"
[tool.ty.src]
include = ["src", "tests"]
exclude = ["src/migrations/"]
# Per-file overrides
[[tool.ty.overrides]]
include = ["tests/**"]
[tool.ty.overrides.rules]
possibly-unresolved-reference = "warn"
Rules Quick Reference
| Rule | Default | Description |
|---|---|---|
possibly-unresolved-reference |
error | Variable might not be defined |
invalid-argument-type |
error | Argument type mismatch |
incompatible-assignment |
error | Assigned value incompatible |
missing-argument |
error | Required argument missing |
unsupported-operator |
error | Operator not supported for types |
invalid-return-type |
error | Return type mismatch |
division-by-zero |
warn | Potential division by zero |
unused-ignore-comment |
warn | Suppression not needed |
redundant-cast |
warn | Cast has no effect |
possibly-unbound-attribute |
warn | Attribute might not exist |
index-out-of-bounds |
warn | Index might be out of range |
Intersection Types (ty Exclusive)
ty has first-class intersection type support:
def output_as_json(obj: Serializable) -> str:
if isinstance(obj, Versioned):
reveal_type(obj) # reveals: Serializable & Versioned
return str({
"data": obj.serialize_json(), # From Serializable
"version": obj.version # From Versioned
})
return obj.serialize_json()
Suppression Comments
# Suppress single rule
x: int = "hello" # type: ignore[incompatible-assignment]
# Suppress multiple
y = risky() # type: ignore[possibly-unresolved-reference, invalid-argument-type]
Reference Documents
For detailed information, see:
| Document | Content |
|---|---|
references/ty_rules_reference.md |
All rules with examples and fixes |
references/typing_cheatsheet.md |
Python typing module quick reference |
references/advanced_patterns.md |
Protocols, generics, type guards, variance |
references/migration_guide.md |
mypy/pyright → ty migration |
references/common_errors.md |
Error solutions with examples |
references/editor_setup/ |
VS Code, Cursor, Neovim setup |