### Run ty without installation using uvx

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Use uvx to quickly get started with ty without a formal installation.

```shell
uvx ty
```

--------------------------------

### Install ty globally with uv

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Install ty globally on your system using the `uv tool install` command.

```shell
uv tool install ty@latest
```

--------------------------------

### Project Directory Structure Example

Source: https://github.com/astral-sh/ty/blob/main/docs/modules.md

An example of a project layout where source code is located in an app directory.

```text
example-pkg
├── README.md
├── pyproject.toml
└── app
    └── example_pkg
        └── __init__.py
```

--------------------------------

### Install ty in Docker

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Install ty in a Docker container by copying the binary from the official Astral ty image.

```dockerfile
COPY --from=ghcr.io/astral-sh/ty:latest /ty /bin/
```

--------------------------------

### Start Ty Language Server

Source: https://github.com/astral-sh/ty/blob/main/docs/editors.md

Use this command to start the Ty language server. Refer to your editor's documentation for instructions on connecting to an LSP server.

```shell
ty server
```

--------------------------------

### Install ty with pip

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Install ty into your current Python environment using pip.

```shell
pip install ty
```

--------------------------------

### Inspect ty installer script on Windows

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Inspect the contents of the ty standalone installer script before execution on Windows using `irm` and `more`.

```pwsh-session
PS> powershell -c "irm https://astral.sh/ty/install.ps1 | more"
```

--------------------------------

### Install ty globally with mise

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Install ty globally using the mise version manager.

```shell
mise install ty
```

--------------------------------

### Install ty on Windows using PowerShell and irm

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Download and execute the ty standalone installer script on Windows using PowerShell's `irm` cmdlet. Ensure your execution policy allows script execution.

```pwsh-session
PS> powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/ty/install.ps1 | iex"
```

--------------------------------

### Install ty on macOS and Linux using curl

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Download and execute the ty standalone installer script using curl.

```console
$ curl -LsSf https://astral.sh/ty/install.sh | sh
```

--------------------------------

### Install ty on macOS and Linux using wget

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Download and execute the ty standalone installer script using wget if curl is not available.

```console
$ wget -qO- https://astral.sh/ty/install.sh | sh
```

--------------------------------

### Install Development Dependencies

Source: https://github.com/astral-sh/ty/blob/main/CONTRIBUTING.md

Install development dependencies using uv and prek hooks for automatic validation on commit.

```shell
uv run --only-group dev --locked prek install
```

--------------------------------

### Inspect ty installer script on macOS and Linux

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Inspect the contents of the ty standalone installer script before execution using `curl` and `less`.

```console
$ curl -LsSf https://astral.sh/ty/install.sh | less
```

--------------------------------

### Install ty globally with pipx

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Install ty globally using the pipx package manager.

```shell
pipx install ty
```

--------------------------------

### Example Python configuration for Ty

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

This TOML snippet shows the configuration for the Python version used by Ty.

```toml
[environment]
python-version = "3.12"

```

--------------------------------

### Install a specific version of ty on Windows

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Request a specific version of ty during installation on Windows by including the version number in the download URL.

```pwsh-session
PS> powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/ty/0.0.56/install.ps1 | iex"
```

--------------------------------

### Install a specific version of ty on macOS and Linux

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Request a specific version of ty during installation by including the version number in the download URL.

```console
$ curl -LsSf https://astral.sh/ty/0.0.56/install.sh | sh
```

--------------------------------

### Explain Ty Help

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/cli.md

Prints help messages for Ty commands. You can specify a subcommand to get its specific help information.

```bash
ty explain help [COMMAND]
```

--------------------------------

### Upgrade globally installed ty with uv

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Update a globally installed ty package using `uv tool upgrade`.

```shell
uv tool upgrade ty
```

--------------------------------

### Configure Extra Paths in ty.toml

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/configuration.md

Specify custom paths for module resolution in ty.toml. Use this for modules not installed conventionally.

```toml
[environment]
extra-paths = ["./shared/my-search-path"]
```

--------------------------------

### Unsupported Operator Example

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

Demonstrates an unsupported operation between two instances of a custom class, which will result in a TypeError.

```python
class A: ...


# TypeError: unsupported operand type(s) for +: 'A' and 'A'
A() + A()  # error
```

--------------------------------

### Unused Awaitable Example

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

Shows a coroutine being called but not awaited, which will trigger a RuntimeWarning. The correct usage with 'await' is also shown.

```python
async def fetch_data() -> str:
    return "data"


async def main() -> None:
    # Warning: coroutine is not awaited
    fetch_data()  # error
    await fetch_data()  # OK
```

--------------------------------

### Configure Multiple Source Roots for Ty in Monorepo

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/typing-faq.md

Define multiple source directories for Ty in a monorepo setup using pyproject.toml. This treats all specified packages as a single project.

```toml
[tool.ty.environment]
root = ["packages/package-a", "packages/package-b"]
```

--------------------------------

### ty check --extra-search-path option

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/cli.md

Add an additional path for module resolution in 'ty check'. Useful for unconventional module installations.

```bash
ty check --extra-search-path <path>
```

--------------------------------

### Upgrade ty with pipx

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Update a globally installed ty package using `pipx upgrade`.

```shell
pipx upgrade ty
```

--------------------------------

### Serve Documentation Locally

Source: https://github.com/astral-sh/ty/blob/main/CONTRIBUTING.md

Run the documentation development server using uvx and mkdocs. The documentation will be available at http://127.0.0.1:8000/ty/.

```shell
uvx --with-requirements docs/requirements.txt -- mkdocs serve -f mkdocs.yml
```

--------------------------------

### Configure Project Root Directories

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/configuration.md

Specify multiple directories to search for first-party modules. Paths are searched in priority order. If unspecified, Ty attempts to detect common project layouts.

```toml
[tool.ty.environment]
# Multiple directories (priority order)
root = ["./src", "./lib", "./vendor"]
```

```toml
[environment]
# Multiple directories (priority order)
root = ["./src", "./lib", "./vendor"]
```

--------------------------------

### Main ty CLI Usage

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/cli.md

The basic command structure for using the 'ty' CLI.

```bash
ty <COMMAND>
```

--------------------------------

### Enable Auto-Import Suggestions (Zed)

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Configure ty to include auto-import suggestions in code completions for Zed.

```json
{
  "lsp": {
    "ty": {
      "settings": {
        "completions": {
          "autoImport": true
        }
      }
    }
  }
}
```

--------------------------------

### Configure include and exclude paths

Source: https://github.com/astral-sh/ty/blob/main/docs/exclusions.md

Define directories to include or exclude from file discovery using project configuration files.

```toml
[tool.ty.src]
include = ["src", "tests"]
exclude = ["src/generated"]
```

```toml
[src]
include = ["src", "tests"]
exclude = ["src/generated"]
```

--------------------------------

### Validate static_assert arguments

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

This Python code shows examples where static_assert fails because its argument is not statically known to be true.

```python
from ty_extensions import static_assert

# evaluates to `False`
static_assert(1 + 1 == 3)  # error

# does not have a statically known truthiness
static_assert(int(2.0 * 3.0) == 6)  # error

```

--------------------------------

### Display help for the 'ty' CLI

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/cli.md

Use this command to view the general help message for the 'ty' CLI. It provides an overview of available commands and their usage.

```bash
ty help [COMMAND]
```

--------------------------------

### Configure Extra Paths in pyproject.toml

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/configuration.md

Specify custom paths for module resolution in pyproject.toml. Use this for modules not installed conventionally.

```toml
[tool.ty.environment]
extra-paths = ["./shared/my-search-path"]
```

--------------------------------

### Configure rule levels via command line

Source: https://github.com/astral-sh/ty/blob/main/docs/rules.md

Use flags to set specific rules to error, warn, or ignore status during execution.

```shell
ty check \
  --warn unused-ignore-comment \        # Make `unused-ignore-comment` a warning
  --ignore redundant-cast \             # Disable `redundant-cast`
  --error possibly-missing-attribute \  # Error on `possibly-missing-attribute`
  --error possibly-missing-import       # Error on `possibly-missing-import`
```

--------------------------------

### Initialize Git Submodules

Source: https://github.com/astral-sh/ty/blob/main/CONTRIBUTING.md

After cloning, initialize and update all git submodules recursively.

```shell
git submodule update --init --recursive
```

--------------------------------

### Incorrect Legacy Positional-Only Parameter

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

This example shows a function where `__y` is intended to be positional-only but is not recognized as such due to incorrect legacy syntax.

```python
# `__y` is not considered positional-only
def f(x, __y):  # error
    pass
```

--------------------------------

### Configure Override Rules with Inclusions

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/configuration.md

Specify file and directory patterns to include for an override. If not specified, defaults to matching all files (`**`).

```toml
[[tool.ty.overrides]]
include = [
    "src",
    "tests",
]
```

```toml
[[overrides]]
include = [
    "src",
    "tests",
]
```

--------------------------------

### Unresolved Import Statement

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

Checks for import statements where the module cannot be resolved, preventing runtime ModuleNotFoundError. Ensure all imported modules are installed and accessible.

```python
# ModuleNotFoundError: No module named 'foo'
import foo  # error
```

--------------------------------

### Configure Custom Typeshed Path

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/configuration.md

Provide an optional path to a custom typeshed directory on disk for standard-library types. Falls back to vendored typeshed stubs if not provided.

```toml
[tool.ty.environment]
typeshed = "/path/to/custom/typeshed"
```

```toml
[environment]
typeshed = "/path/to/custom/typeshed"
```

--------------------------------

### Specify ty configuration file in Neovim (<0.11)

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Configure the path to ty's configuration file using the lspconfig plugin for Neovim versions prior to 0.11.

```lua
require('lspconfig').ty.setup({
  settings = {
    ty = {
      configurationFile = "./.config/ty.toml"
    },
  },
})
```

--------------------------------

### Invalid string annotation syntax

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

Use a valid Python expression within the string literal for forward references. This example shows an incorrect usage.

```python
def foo() -> "instance of C":  # error
    return 42


class C: ...
```

--------------------------------

### Enable Auto-Import Suggestions (Neovim)

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Configure ty to include auto-import suggestions in code completions for Neovim. Supports versions >=0.11 and <0.11.

```lua
-- Neovim >=0.11:
vim.lsp.config('ty', {
  settings = {
    ty = {
      completions = {
        autoImport = true,
      },
    },
  },
})

-- Neovim <0.11:
require('lspconfig').ty.setup({
  settings = {
    ty = {
      completions = {
        autoImport = true,
      },
    },
  },
})
```

--------------------------------

### Subclassing Dataclass with Order=True

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

This example demonstrates a class inheriting from a dataclass where `order=True`. This pattern is flagged because it can cause `TypeError` at runtime when comparing instances of the parent and child classes.

```python
from dataclasses import dataclass


@dataclass(order=True)
class Parent:
    value: int


class Child(Parent):  # error
    pass


# At runtime, this raises TypeError:
# Child(1) < Parent(2)
```

--------------------------------

### Enable fish shell autocompletion for ty

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Add ty shell autocompletion for fish to your `~/.config/fish/completions/ty.fish` file.

```fish
echo 'ty generate-shell-completion fish | source' > ~/.config/fish/completions/ty.fish
```

--------------------------------

### Python Type Variable Bound Examples

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

Illustrates invalid type variable bounds where the bound itself references a type variable. Type variable bounds must be concrete types.

```python
from typing import TypeVar

# error: [invalid-type-variable-bound]
RecursiveT = TypeVar("RecursiveT", bound=list["RecursiveT"])
U = TypeVar("U")
# error: [invalid-type-variable-bound]
BoundT = TypeVar("BoundT", bound=U)


def f[T: list[T]](): ...  # error: [invalid-type-variable-bound]
def g[U, T: U](): ...  # error: [invalid-type-variable-bound]
```

--------------------------------

### Configure Project Root

Source: https://github.com/astral-sh/ty/blob/main/docs/modules.md

Configuration settings to define the project root directory when using a non-standard layout.

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

```toml
[environment]
root = ["./app"]
```

--------------------------------

### Runtime Error Example from Invariance Violation

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/typing-faq.md

Shows a potential runtime error when code expects `Directory` objects but receives a `File` object due to a prior invariance violation.

```Python
for directory in directories:
    directory.children()  # runtime: 'File' object has no attribute 'children'
```

--------------------------------

### Configure ty rules in Neovim (<0.11)

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Configure ty's rules using the lspconfig plugin for Neovim versions prior to 0.11.

```lua
require('lspconfig').ty.setup({
  settings = {
    ty = {
      configuration = {
        rules = {
          ["unresolved-reference"] = "warn"
        }
      }
    }
  },
})
```

--------------------------------

### Enum member with explicit type annotation (error)

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

This example shows an enum member 'DOG' with an explicit type annotation 'int', which is flagged as an error by the rule. Enum members should not be annotated.

```python
from enum import Enum


class Pet(Enum):
    CAT = 1  # OK
    # enum members should not be annotated
    DOG: int = 2  # error
```

--------------------------------

### Run ty with uvx

Source: https://github.com/astral-sh/ty/blob/main/docs/index.md

Use uvx to quickly run ty for checking Python files. ty checks all Python files in the working directory or project by default.

```shell
uvx ty check
```

--------------------------------

### Build Python Package

Source: https://github.com/astral-sh/ty/blob/main/CONTRIBUTING.md

Build the Python package using uv. Maturin is used as the build backend.

```shell
uv build
```

--------------------------------

### Valid and invalid TypeAliasType creation

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

This example illustrates the correct and incorrect ways to create `TypeAliasType` instances. It shows that the name provided to `TypeAliasType` must be a string literal, not a variable or function call.

```python
from typing import TypeAliasType


def get_name() -> str:
    return "NewAlias"


IntOrStr = TypeAliasType("IntOrStr", int | str)  # okay
# TypeAliasType name must be a string literal
NewAlias = TypeAliasType(get_name(), int)  # error
```

--------------------------------

### Corrected enum member without annotation

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

This example demonstrates the correct way to define enum members without explicit type annotations, allowing type checkers to infer the literal type.

```python
from enum import Enum


class Pet(Enum):
    CAT = 1
    DOG = 2
```

--------------------------------

### Invoke ty using uv run

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

After adding ty as a dependency, use `uv run` to invoke it.

```shell
uv run ty
```

--------------------------------

### Type Assertion Failure in Python

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

This example shows the correct and incorrect usage of `assert_type`. The incorrect usage occurs when the actual type of a variable does not match the type asserted in the `assert_type` call, leading to an error.

```python
from typing import assert_type

def _(x: int):
    assert_type(x, int)  # fine
    # Actual type does not match asserted type
    assert_type(x, str)  # error
```

--------------------------------

### Set all rules to error in configuration files

Source: https://github.com/astral-sh/ty/blob/main/docs/rules.md

Configure all rules to a specific level globally within the configuration file.

```toml
[tool.ty.rules]
all = "error"
```

```toml
[rules]
all = "error"
```

--------------------------------

### Python Invalid Attribute Access Examples

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

Demonstrates correct and incorrect assignments to class variables and instance-only variables in Python. Use this snippet to understand the rule's behavior with different assignment scenarios.

```python
from typing import ClassVar


class C:
    instance_var: int
    class_var: ClassVar[int] = 1

    def __init__(self):
        # instance variable declared in the class body
        self.instance_var = 42

        # instance-only variable not declared in the class body
        self.instance_only_var: int = 42


C.class_var = 3  # okay

C.instance_var = 56  # okay
C().instance_var = 72  # okay

C().instance_only_var = 100  # okay

# Cannot assign to class variable from instance
C().class_var = 3  # error

# Cannot assign to instance-only variable from class
C.instance_only_var = 56  # error
```

--------------------------------

### Enable ty Language Server in Neovim (<0.11)

Source: https://github.com/astral-sh/ty/blob/main/docs/editors.md

Configure older versions of Neovim (<0.11) to use ty as a language server via nvim-lspconfig. This requires an older version of the nvim-lspconfig extension.

```lua
require('lspconfig').ty.setup({
  settings = {
    ty = {
      -- ty language server settings go here
    }
  }
})
```

--------------------------------

### Configure Ty Import Strategy in VS Code

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Set the strategy for loading the ty executable. Use 'useBundled' to ensure the extension's bundled version is used.

```json
{
  "ty.importStrategy": "useBundled"
}
```

--------------------------------

### Disallow Underscore Prefix for NamedTuple Fields

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

Field names in NamedTuple classes cannot start with an underscore. This rule prevents potential naming conflicts and ensures valid field definitions, avoiding runtime ValueErrors.

```python
>>> from typing import NamedTuple
>>> class Foo(NamedTuple):
...     _bar: int
ValueError: Field names cannot start with an underscore: '_bar'
```

--------------------------------

### Enable Auto-Import Suggestions

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Configure ty to include auto-import suggestions in code completions. Allows completion of symbols not currently in scope.

```json
{
  "ty.completions.autoImport": true
}
```

--------------------------------

### Assert type with unspellable subtype

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

This example demonstrates an assert_type() call where the actual type is an unspellable subtype of the asserted type. This occurs when ty infers a more precise type than can be expressed in user annotations, leading to a potential type assertion failure.

```python
from typing import assert_type

def _(x: int):
    assert_type(x, int)  # fine
    if x:
        # the actual type is `int & ~AlwaysFalsy`,
        # which excludes types like `Literal[0]`
        # error: [assert-type-unspellable-subtype]
        assert_type(x, int)
```

--------------------------------

### Home Assistant Benchmark Results

Source: https://github.com/astral-sh/ty/blob/main/BENCHMARKS.md

This snippet presents benchmark results for 'ty' and other tools on the 'Home Assistant' project. It highlights performance differences and comparative speeds.

```text
homeassistant
-------------

Benchmark 1: ty
  Time (mean ± σ):      1.812 s ±  0.033 s    [User: 23.009 s, System: 2.224 s]
  Range (min … max):    1.782 s …  1.873 s    10 runs
 
  Warning: Ignoring non-zero exit code. 

Benchmark 2: Pyrefly
  Time (mean ± σ):      2.550 s ±  0.039 s    [User: 23.491 s, System: 4.450 s]
  Range (min … max):    2.502 s …  2.624 s    10 runs
 
  Warning: Ignoring non-zero exit code. 

Benchmark 3: mypy
  Time (mean ± σ):     24.601 s ±  0.141 s    [User: 45.118 s, System: 4.172 s]
  Range (min … max):   24.340 s … 24.846 s    10 runs
 
Benchmark 4: Pyright
  Time (mean ± σ):     23.410 s ±  0.483 s    [User: 323.789 s, System: 22.983 s]
  Range (min … max):   22.596 s … 23.994 s    10 runs
 
  Warning: Ignoring non-zero exit code. 

Summary
  ty ran
    1.41 ± 0.03 times faster than Pyrefly
   12.92 ± 0.36 times faster than Pyright
   13.57 ± 0.26 times faster than mypy

-------------------------------------------------------------------------------

```

--------------------------------

### Python Type Guard Definition Examples

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

Demonstrates incorrect definitions for type guard functions. Type guards must have at least one positional argument. This includes cases with no parameters, only keyword-only parameters, variadic arguments, or only `self`/`cls` in methods.

```python
from typing import TypeIs


# no parameter
def f() -> TypeIs[int]:  # error
    return True


# no positional arguments allowed
def f(*, v: object) -> TypeIs[int]:  # error
    return True


# expected variadic arguments
def f(*args: object) -> TypeIs[int]:  # error
    return True


class C:
    # only positional argument is `self`
    def f(self) -> TypeIs[int]:  # error
        return True
```

--------------------------------

### Type Checking PEP 723 Inline-Metadata Scripts with ty

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/typing-faq.md

Use this command to type check a single Python script that includes PEP 723 inline metadata. The `--with-requirements` flag ensures that dependencies specified in the script's header are installed.

```bash
uvx --with-requirements script.py ty check script.py
```

--------------------------------

### Specify ty configuration file in Neovim (>=0.11)

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Configure the path to ty's configuration file using the Lua API for Neovim versions 0.11 and later.

```lua
vim.lsp.config('ty', {
  settings = {
    ty = {
      configurationFile = "./.config/ty.toml"
    },
  },
})
```

--------------------------------

### Include files and directories in ty.toml

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/configuration.md

Specify files and directories to include for type checking in ty.toml. This setting is overridden by 'exclude'.

```toml
[src]
include = [
    "src",
    "tests",
]
```

--------------------------------

### Abstract method in final class example

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

This snippet demonstrates a final class 'Derived' that inherits from an abstract base class 'Base' but fails to implement the abstract method 'method'. This violates the rule, as a final class cannot be subclassed to implement missing abstract methods.

```python
from abc import ABC, abstractmethod
from typing import final


class Base(ABC):
    @abstractmethod
    def method(self) -> int: ...


@final
# `Derived` does not implement `method`
class Derived(Base):  # error
    pass

```

--------------------------------

### Configure Ty Log File in Neovim

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Set the log file path for the Ty language server in Neovim. This is configured within the 'init_options' for the LSP client.

```lua
-- Neovim >=0.11:
vim.lsp.config('ty', {
  init_options = {
    logFile = '/path/to/ty.log',
  },
})

-- Neovim <0.11:
require('lspconfig').ty.setup({
  init_options = {
    logFile = '/path/to/ty.log',
  },
})
```

--------------------------------

### Enable ty Language Server in Neovim (>=0.11)

Source: https://github.com/astral-sh/ty/blob/main/docs/editors.md

Configure Neovim to use ty as a language server using nvim-lspconfig. This snippet shows how to enable the server and optionally configure its settings.

```lua
-- Optional: Only required if you need to update the language server settings
vim.lsp.config('ty', {
  settings = {
    ty = {
      -- ty language server settings go here
    }
  }
})

-- Required: Enable the language server
vim.lsp.enable('ty')
```

--------------------------------

### Python Version Conditional Syntax and Symbols

Source: https://github.com/astral-sh/ty/blob/main/docs/python-version.md

Demonstrates how to use Python 3.10+ syntax like 'match' statements and access version-specific symbols like 'sys.stdlib_module_names'. Shows how to guard newer features with version checks to maintain compatibility with older Python versions.

```python
import sys

# `invalid-syntax` error if `python-version` is set to 3.9 or lower:
match "echo hello".split():
    case ["echo", message]:
        print(message)
    case _:
        print("unknown command")

# `unresolved-attribute` error if `python-version` is set to 3.9 or lower:
print(sys.stdlib_module_names)

if sys.version_info >= (3, 10):
    # ok, because the usage is guarded by a version check:
    print(sys.stdlib_module_names)
```

--------------------------------

### Configure ty rules in Neovim (>=0.11)

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Configure ty's rules using the Lua API for Neovim versions 0.11 and later.

```lua
vim.lsp.config('ty', {
  settings = {
    ty = {
      configuration = {
        rules = {
          ["unresolved-reference"] = "warn"
        }
      }
    }
  },
})
```

--------------------------------

### Configure rule levels in configuration files

Source: https://github.com/astral-sh/ty/blob/main/docs/rules.md

Define rule levels within project configuration files for persistent settings.

```toml
[tool.ty.rules]
unused-ignore-comment = "warn"
redundant-cast = "ignore"
possibly-missing-attribute = "error"
possibly-missing-import = "error"
```

```toml
[rules]
unused-ignore-comment = "warn"
redundant-cast = "ignore"
possibly-missing-attribute = "error"
possibly-missing-import = "error"
```

--------------------------------

### Format Markdown Files

Source: https://github.com/astral-sh/ty/blob/main/CONTRIBUTING.md

Format all markdown files in the repository using Prettier to ensure consistent style.

```shell
npx prettier --prose-wrap always --write "**/*.md"
```

--------------------------------

### Explain Ty Rules

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/cli.md

Provides explanations for Ty rules. You can specify a particular rule or omit it to explain all rules. The output format can be text or JSON.

```bash
ty explain rule [OPTIONS] [RULE]
```

```bash
ty explain rule --output-format json
```

--------------------------------

### Set project root in ty.toml

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/configuration.md

Specify the project root directory in ty.toml using the 'root' option. This option is deprecated in favor of 'environment.root'.

```toml
[src]
root = "./app"
```

--------------------------------

### General Benchmark Results for ty

Source: https://github.com/astral-sh/ty/blob/main/BENCHMARKS.md

This benchmark shows the mean execution time and standard deviation for 'ty' compared to Pyrefly, mypy, and Pyright. It indicates 'ty' is significantly faster than Pyright and mypy, and slightly faster than Pyrefly.

```text
Benchmark 1: ty
  Time (mean ± σ):      1.216 s ±  0.042 s    [User: 14.994 s, System: 0.766 s]
  Range (min … max):    1.157 s …  1.293 s    10 runs
 
  Warning: Ignoring non-zero exit code. 

Benchmark 2: Pyrefly
  Time (mean ± σ):      1.492 s ±  0.025 s    [User: 12.424 s, System: 1.053 s]
  Range (min … max):    1.451 s …  1.519 s    10 runs
 
  Warning: Ignoring non-zero exit code. 

Benchmark 3: mypy
  Time (mean ± σ):     28.227 s ±  0.074 s    [User: 27.631 s, System: 0.580 s]
  Range (min … max):   28.137 s … 28.342 s    10 runs
 
  Warning: Ignoring non-zero exit code. 

Benchmark 4: Pyright
  Time (mean ± σ):     16.885 s ±  0.505 s    [User: 231.071 s, System: 9.429 s]
  Range (min … max):   16.283 s … 17.933 s    10 runs
 
  Warning: Ignoring non-zero exit code. 

Summary
  ty ran
    1.23 ± 0.05 times faster than Pyrefly
   13.89 ± 0.63 times faster than Pyright
   23.22 ± 0.80 times faster than mypy
```

--------------------------------

### Black Benchmark Results

Source: https://github.com/astral-sh/ty/blob/main/BENCHMARKS.md

This snippet shows the benchmark results for 'ty' and other tools on the 'Black' project. It includes mean time, standard deviation, and run counts.

```text
black
-----

Benchmark 1: ty
  Time (mean ± σ):      69.5 ms ±   1.6 ms    [User: 530.8 ms, System: 34.8 ms]
  Range (min … max):    65.7 ms …  73.6 ms    40 runs
 
  Warning: Ignoring non-zero exit code. 

Benchmark 2: Pyrefly
  Time (mean ± σ):     128.3 ms ±   2.5 ms    [User: 465.1 ms, System: 53.0 ms]
  Range (min … max):   123.4 ms … 134.3 ms    23 runs
 
  Warning: Ignoring non-zero exit code. 

Benchmark 3: mypy
  Time (mean ± σ):      1.316 s ±  0.012 s    [User: 1.216 s, System: 0.092 s]
  Range (min … max):    1.303 s …  1.336 s    10 runs
 
Benchmark 4: Pyright
  Time (mean ± σ):      1.420 s ±  0.010 s    [User: 18.088 s, System: 0.981 s]
  Range (min … max):    1.404 s …  1.433 s    10 runs
 
  Warning: Ignoring non-zero exit code. 

Summary
  ty ran
    1.85 ± 0.06 times faster than Pyrefly
   18.94 ± 0.46 times faster than mypy
   20.45 ± 0.49 times faster than Pyright

-------------------------------------------------------------------------------

```

--------------------------------

### Set all rules to error via command line

Source: https://github.com/astral-sh/ty/blob/main/docs/rules.md

Apply a global rule level to all checks using the all keyword.

```shell
ty check --error all
```

--------------------------------

### Clone TY Repository

Source: https://github.com/astral-sh/ty/blob/main/CONTRIBUTING.md

Use this command to clone the TY repository from GitHub.

```shell
git clone https://github.com/astral-sh/ty.git
```

--------------------------------

### Configure Override Rules with Exclusions

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/configuration.md

Define file and directory patterns to exclude from an override. Exclude patterns take precedence over include patterns within the same override. Defaults to excluding no files.

```toml
[[tool.ty.overrides]]
exclude = [
    "generated",
    "*.proto",
    "tests/fixtures/**",
    "!tests/fixtures/important.py"  # Include this one file
]
```

```toml
[[overrides]]
exclude = [
    "generated",
    "*.proto",
    "tests/fixtures/**",
    "!tests/fixtures/important.py"  # Include this one file
]
```

--------------------------------

### Enable Elvish shell autocompletion for ty

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Add ty shell autocompletion for Elvish to your `~/.elvish/rc.elv` file.

```elvish
echo 'eval (ty generate-shell-completion elvish | slurp)' >> ~/.elvish/rc.elv
```

--------------------------------

### Configure Python version for experimental syntax

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

Specify the Python version to enable experimental syntax checks. This is useful for testing upcoming language features.

```toml
[environment]
python-version = "3.14"
```

--------------------------------

### Ignore virtual environment files

Source: https://github.com/astral-sh/ty/blob/main/docs/exclusions.md

Create a .gitignore file within a virtual environment directory to prevent ty from emitting diagnostics for those files.

```shell
echo "*" > .venv/.gitignore
```

--------------------------------

### Display Ty Version

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/cli.md

Displays the current version of Ty. The output format can be specified as plain text or JSON.

```bash
ty version [OPTIONS]
```

```bash
ty version --output-format json
```

--------------------------------

### Specify ty configuration file in Zed

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Set the path to ty's configuration file within the Zed editor's LSP settings.

```json
{
  "lsp": {
    "ty": {
      "settings": {
        "configurationFile": "./.config/ty.toml"
      }
    }
  }
}
```

--------------------------------

### Configure Project Root for Ty

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/typing-faq.md

Specify non-root source directories for Ty when your code is not in the project root or src/ directory. This is configured in pyproject.toml.

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

--------------------------------

### Exclude files and directories in ty.toml

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/configuration.md

Configure patterns to exclude files and directories from type checking in ty.toml. Supports .gitignore-like syntax, including negation.

```toml
[src]
exclude = [
    "generated",
    "*.proto",
    "tests/fixtures/**",
    "!tests/fixtures/important.py"  # Include this one file
]
```

--------------------------------

### Enable Function Parentheses Insertion (Zed)

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Configure ty to automatically insert parentheses for completions in Zed.

```json
{
  "lsp": {
    "ty": {
      "settings": {
        "completions": {
          "completeFunctionParentheses": true
        }
      }
    }
  }
}
```

--------------------------------

### isort Benchmark Results

Source: https://github.com/astral-sh/ty/blob/main/BENCHMARKS.md

This snippet shows the benchmark results for 'ty' and other tools on the 'isort' project. It includes performance metrics and comparative speed.

```text
isort
-----


```

--------------------------------

### Add ty as a development dependency using uv

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Add ty as a development dependency to your project using uv. This ensures all developers use the same version.

```shell
uv add --dev ty
```

--------------------------------

### Set ty globally with mise

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Configure mise to use ty globally.

```shell
mise use --global ty
```

--------------------------------

### Configure Ty Log File in Zed

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Define the log file path for the Ty language server within Zed's LSP configuration.

```json
{
  "lsp": {
    "ty": {
      "initialization_options": {
        "logFile": "/path/to/ty.log"
      }
    }
  }
}
```

--------------------------------

### Run Ty Per-Package in Monorepo

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/typing-faq.md

Execute Ty's check command for individual packages within a monorepo. Use the --project flag to specify the target package directory.

```bash
ty check --project packages/package-a
ty check --project packages/package-b
```

--------------------------------

### Specify ty configuration file in VS Code

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Set the path to a custom ty.toml configuration file in VS Code. This overrides any discovered configurations.

```json
{
  "ty.configurationFile": "./.config/ty.toml"
}
```

--------------------------------

### Conditional Reachability for Dependency Version Compatibility

Source: https://github.com/astral-sh/ty/blob/main/docs/features/type-system.md

Shows how ty's reachability analysis allows code to be type-checked against different dependency versions by evaluating version-specific conditions at type-checking time.

```python
import pydantic
from pydantic import BaseModel

PYDANTIC_V2 = pydantic.__version__.startswith("2.")

class Person(BaseModel):
    name: str

def to_json(person: Person):
    if PYDANTIC_V2:
        return person.model_dump_json()  # no error here when checking with 1.x
    else:
        return person.json()
```

--------------------------------

### Enable Zsh shell autocompletion for ty

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Add ty shell autocompletion for Zsh to your `~/.zshrc` file.

```bash
echo 'eval "$(ty generate-shell-completion zsh)"' >> ~/.zshrc
```

--------------------------------

### Correct string annotation syntax

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/rules.md

This demonstrates the correct way to use string literals for forward references, ensuring the string can be parsed as a Python expression.

```python
def foo() -> "C":
    return C()


class C: ...
```

--------------------------------

### Enable PowerShell/pwsh shell autocompletion for ty

Source: https://github.com/astral-sh/ty/blob/main/docs/installation.md

Add ty shell autocompletion for PowerShell/pwsh to your `$PROFILE` file. This script ensures the profile file exists and appends the autocompletion command.

```powershell
if (!(Test-Path -Path $PROFILE)) {
  New-Item -ItemType File -Path $PROFILE -Force
}
Add-Content -Path $PROFILE -Value '(& ty generate-shell-completion powershell) | Out-String | Invoke-Expression'
```

--------------------------------

### Enable Function Parentheses Insertion (Neovim)

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/editor-settings.md

Configure ty to automatically insert parentheses for completions in Neovim. Supports versions >=0.11 and <0.11.

```lua
-- Neovim >=0.11:
vim.lsp.config('ty', {
  settings = {
    ty = {
      completions = {
        completeFunctionParentheses = true,
      },
    },
  },
})

-- Neovim <0.11:
require('lspconfig').ty.setup({
  settings = {
    ty = {
      completions = {
        completeFunctionParentheses = true,
      },
    },
  },
})
```

--------------------------------

### Include files and directories in pyproject.toml

Source: https://github.com/astral-sh/ty/blob/main/docs/reference/configuration.md

Specify files and directories to include for type checking in pyproject.toml. This setting is overridden by 'exclude'.

```toml
[tool.ty.src]
include = [
    "src",
    "tests",
]
```