https://github.com/wemake-services/mypy-extras

A collection of extra types and features for mypy
https://github.com/wemake-services/mypy-extras

Last synced: 4 months ago
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A collection of extra types and features for mypy

• Host: GitHub
• URL: https://github.com/wemake-services/mypy-extras
• Owner: wemake-services
• License: mit
• Created: 2020-10-31T10:50:14.000Z (almost 5 years ago)
• Default Branch: master
• Last Pushed: 2025-05-02T02:34:55.000Z (5 months ago)
• Last Synced: 2025-06-03T09:46:12.955Z (4 months ago)
• Language: Python
• Size: 908 KB
• Stars: 34
• Watchers: 3
• Forks: 0
• Open Issues: 14
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • Contributing: CONTRIBUTING.md
  • License: LICENSE

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README

          
# mypy-extras

[![wemake.services](https://img.shields.io/badge/%20-wemake.services-green.svg?label=%20&logo=data%3Aimage%2Fpng%3Bbase64%2CiVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAMAAAAoLQ9TAAAABGdBTUEAALGPC%2FxhBQAAAAFzUkdCAK7OHOkAAAAbUExURQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAP%2F%2F%2F5TvxDIAAAAIdFJOUwAjRA8xXANAL%2Bv0SAAAADNJREFUGNNjYCAIOJjRBdBFWMkVQeGzcHAwksJnAPPZGOGAASzPzAEHEGVsLExQwE7YswCb7AFZSF3bbAAAAABJRU5ErkJggg%3D%3D)](https://wemake.services)

[![test](https://github.com/wemake-services/mypy-extras/workflows/test/badge.svg?branch=master&event=push)](https://github.com/wemake-services/mypy-extras/actions?query=workflow%3Atest)

[![codecov](https://codecov.io/gh/wemake-services/mypy-extras/branch/master/graph/badge.svg)](https://codecov.io/gh/wemake-services/mypy-extras)

[![Python Version](https://img.shields.io/pypi/pyversions/mypy-extras.svg)](https://pypi.org/project/mypy-extras/)

[![wemake-python-styleguide](https://img.shields.io/badge/style-wemake-000000.svg)](https://github.com/wemake-services/wemake-python-styleguide)

## Features

- Provides a custom `mypy` plugin to enhance its possibilities

- Provides new types that can be used in your programs with our plugin

- Fully typed with annotations and checked with mypy, [PEP561 compatible](https://www.python.org/dev/peps/pep-0561/)

## Installation

```bash

pip install mypy-extras

```

You also need to [configure](https://mypy.readthedocs.io/en/stable/config_file.html)

`mypy` correctly and install our custom plugin:

```ini

# In setup.cfg or mypy.ini:

[mypy]

plugins =

  mypy_extras.plugin.entrypoint

```

We also recommend to use the same `mypy` settings [we use](https://github.com/wemake-services/wemake-python-styleguide/blob/master/styles/mypy.toml).

## Usage

### AttrOf

We provide a special type to get named attributes of other types, like so:

```python

from typing_extensions import Literal  # or typing on python3.8+

from mypy_extras import AttrOf

class User(object):

    def auth(self, username: str, password: str) -> bool:

        return False  # Just an example

def get_callback(user: User) -> AttrOf[User, Literal['auth']]:

    return user.auth

user: User

reveal_type(get_callback(user))

# Revealed type is "def (username: builtins.str, password: builtins.str) -> builtins.bool"

```

### ensure_attr

We can ensure that some `str` attribute exists on a object:

```python

from mypy_extras import ensure_attr

class User(object):

    policy = 'update'

reveal_type(ensure_attr(User, 'policy'))  # Revealed type is 'Literal['policy']'

reveal_type(ensure_attr(User, 'missing'))  # Error: attribute "missing" does not exist on type "User"

```

It is useful when we do any manipulations with objects based on a string field:

```python

DEFAULT_POLICY_FIELD: Final = ensure_attr(User, 'policy')  # typesafe

# vs

DEFAULT_POLICY_FIELD: Final = 'policy'  

# User can rename the field, and this will blow now!

```

## License

[MIT](https://github.com/wemake.services/mypy-extras/blob/master/LICENSE)