# Python Attrs Module

`attrs` is the Python package that will bring back the joy of writing classes by relieving you from the drudgery of implementing the object protocol (methods like `__init__`, `__repr__`, `__eq__`, etc.).

*Note: Python 3.7+ introduced `dataclasses`, which are similar but less powerful than `attrs`.*

## Installation

```bash
pip install attrs
```

## Basic Usage

Use the `@define` decorator (modern alias for `@attr.s`) to declare a class.

```python
from attrs import define

@define
class Point:
    x: int
    y: int

p = Point(1, 2)
print(p)
# Output: Point(x=1, y=2)
print(p == Point(1, 2))
# Output: True
```

## Validation

You can add validators to fields.

```python
from attrs import define, field, validators

@define
class User:
    email: str = field(validator=validators.instance_of(str))
    age: int = field(validator=validators.ge(18))

# User(email="test", age=10) # Raises ValueError
```

## Converters

Converters run automatically when setting a value.

```python
from attrs import define, field

@define
class Coordinates:
    x: int = field(converter=int)
    y: int = field(converter=int)

c = Coordinates("1", 2.5)
print(c)
# Output: Coordinates(x=1, y=2)
```

## Immutability (Frozen Classes)

You can easily make instances immutable.

```python
from attrs import define

@define(frozen=True)
class Config:
    host: str
    port: int

c = Config("localhost", 8080)
# c.port = 9000 # Raises attr.exceptions.FrozenInstanceError
```

[[programming/python/python]]