attrs-mate 0.0.3

A plugin extends power of attrs library.

---

Welcome to attrs_mate Documentation

attrs might be the second widely used python library for developers (First is requests). It is the ultimate weapon for writing class.

attrs_mate aims to bring more features to attrs, and better code pattern.

Usage1: More Utility Methods

from attrs_mate import attr, AttrsClass

@attr.s
class User(AttrsClass):
    id = attr.ib()
    name = attr.ib()

user = User(id=1, name="Alice")
user.keys() # ["id", "name"]
user.values() # [1, "Alice"]
user.items() # [("id", 1), ("name": "Alice")]
user.to_dict() # {"id": 1, "name": "Alice"}
user.to_OrderedDict() # OrderedDict([("id", 1), ("name": "Alice")])

Usage2: Allow attrs to construct complex object from dict data.

Plus, this is an example of nesting schema.

import attr
from attrs_mate import AttrsClass


@attr.s
class Profile(AttrsClass):
    """
    firstname, lastname, ssn are generic data type field.
    """
    firstname = attr.ib(default=None)
    lastname = attr.ib(default=None)
    ssn = attr.ib(default=None)


@attr.s
class Degree(AttrsClass):
    name = attr.ib(default=None)
    year = attr.ib(default=None)


@attr.s
class People(AttrsClass):
    """
    - ``profile`` is nested field.
    - ``degrees`` is collection type field.
    """
    id = attr.ib(default=None)
    profile = attr.ib(
        converter=Profile.from_dict,
        validator=attr.validators.optional(
            attr.validators.instance_of(Profile)
        ),
        factory=Profile,
    )
    degrees = attr.ib(
        converter=lambda degrees: [
            Degree.from_dict(degree) for degree in degrees],
        factory=list,
    )

people = People(
    id=1,
    profile=Profile(
        firstname="David",
        lastname="John",
        ssn="123-45-6789",
    ),
    degrees=[
        Degree(name="Bachelor", year=2004),
        Degree(name="Master", year=2006),
    ],
)

>>> people_data = people.to_dict()
>>> people_data
{
    'id': 1,
    'profile': {
        'lastname': 'John', 'ssn': '123-45-6789', 'firstname': 'David'
    },
    'degrees': [
        {'name': 'Bachelor', 'year': 2004},
        {'name': 'Master', 'year': 2006}
    ]
}

>>> people = People.from_dict(people_data)
>>> people
People(id=1, profile=Profile(firstname='David', lastname='John', ssn='123-45-6789'), degrees=[Degree(name='Bachelor', year=2004), Degree(name='Master', year=2006)])

Usage3: Cached Instance and Property Attribute

from attrs_mate import attr, LazyClass

@attr.s
class User(LazyClass): # instance are cached
    id = attr.ib()
    lastname = attr.ib()
    firstname = attr.ib()
    uuid_called_count = attr.ib(default=0)
    fullname_called_count = attr.ib(default=0)

    @LazyClass.lazyproperty
    def uuid(self):
        self.uuid_called_count += 1
        return self.id

    @LazyClass.lazyproperty
    def fullname(self): # property method are cached
        self.fullname_called_count += 1
        return "{} {}".format(self.lastname, self.firstname)

>>> user1 = User.lazymake(id=1, lastname="David", firstname="John")
>>> user1.fullname_called_count
0 # initially, fullname never been called
>>> user1.fullname
David John
>>> user1.fullname_called_count
1 # called once
>>> user1.fullname
David John
>>> user1.fullname_called_count
1 # User.fullname() not been called

# use factory method to create new instance
>>> user2 = User.lazymake(id=1, lastname="David", firstname="Kim")
>>> id(user1) == id(user2)
True # since
>>> user2.firstname == "John"
True
>>> user2.fullname_called_count
1 # already been called once, because it is actually user1

Install

attrs_mate is released on PyPI, so all you need is:

$ pip install attrs_mate

To upgrade to latest version:

$ pip install --upgrade attrs_mate