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Decorator to add __slots__ in dataclasses

Project description

dataslots

Build Status codecov

PyPI - Python Version PyPI - Status license

Decorator for adding slots

Python3.7 provides dataclasses module for faster class creation (PEP 557). Unfortunately there's no support for __slots__. If you want to create more memory efficient instances, you need to do it by yourself or use dataslots.with_slots decorator.

Usage

Simple example

@with_slots
@dataclass
class Point2D:
    x: int
    y: int

Inheritance

As described in docs, in derived class __dict__ is created, because base class does not have __slots__. Slots are created from all defined properties (returned by dataclasses.fields() function).

@dataclass
class Base:
    a: int


@with_slots
@dataclass
class Derived(Base):
    c: int
    d: int

Dynamic assignment of new variables

@with_slots(add_dict=True)
@dataclass
class Point2D:
    x: int
    y: int
    
point = Point2D(10, 20)
point.length = math.sqrt(point.x ** 2 + point.y ** 2)

Weakref

@with_slots(add_weakref=True)
@dataclass
class Point2D:
    x: int
    y: int
    
point = Point2D(10, 20)
r = weakref.ref(point)

Read-only class variables

With __slots__ it's possible to define read-only class variables. When using dataclasses you cannot provide type for attribute or use typing.ClassVar to declare one.

@with_slots
@dataclass
class A:
    x = 5
    y: ClassVar[set] = set()

More about __slots__

Project details


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dataslots-1.0.1.tar.gz (2.7 kB) Copy SHA256 hash SHA256 Source None

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