# dataslots
[](https://pypi.org/project/dataslots/)
[](https://pypi.org/project/dataslots/)
[](https://github.com/starhel/dataslots/actions)
[](https://github.com/starhel/dataslots/actions)
[](https://slsa.dev)
## Decorator for adding __slots__
In python 3.7 dataclasses module was introduced for faster class creation ([PEP 557](https://www.python.org/dev/peps/pep-0557/)).
Unfortunately, there's no support for `__slots__` (basic support was added in 3.10). If you want to create more memory
efficient instances, you need to do it by yourself or use `@dataslots` decorator.
## Usage
### Simple example
```python
@dataslots
@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).
```python
@dataclass
class Base:
a: int
@dataslots
@dataclass
class Derived(Base):
c: int
d: int
```
### Dynamic assignment of new variables
```python
@dataslots(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
```python
@dataslots(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.
```python
@dataslots
@dataclass
class A:
x = 5
y: ClassVar[set] = set()
```
### Pickling frozen dataclass
Because of an [issue 36424](https://bugs.python.org/issue36424) you need custom `__setstate__` method. In dataslots
there is implemented default version, and it is used if decorated class has no `__getstate__` and `__setstate__`
function declared.
_Added in 1.0.2_
### Data descriptors
[Data descriptors](https://docs.python.org/3.7/howto/descriptor.html#descriptor-protocol) are supported by
inheritance from `DataDescriptor` (base class with required interface) or `DataslotsDescriptor` (class with
additional features to simplify descriptor definition).
Check example directory for basic usage.
_Added in 1.1.0_
### Typing support (PEP 561)
The package is PEP 561 compliant, so you can easily use it with mypy<sup>1</sup> and pyright.
<sup>1</sup> Due to some issues in mypy not all features are supported correctly (like [dataclass alike
interface](https://github.com/python/mypy/issues/14293) or [descriptors](https://github.com/python/mypy/issues/13856)).
_Added in 1.2.0_
### Backport
If you prefer using the newest `dataclasses.dataclass` interface you can use `dataslots.dataclass` wrapper
to provide a consistent interface regardless of the python version.
Notice: Wrapper always uses `dataslots` to make all additional features available and `slots=True` is obligatory.
_Added in 1.2.0_
## SLSA support
All packages from version 1.2.0 can be verified using [SLSA provenance](https://slsa.dev/provenance/v0.2)
(dataslots package is compliant with [SLSA Level 3](https://slsa.dev/spec/v0.1/levels)).
If you want to verify dataslots before installing, you need to download
[SLSA verifier](https://github.com/slsa-framework/slsa-verifier) and run:
```bash
slsa-verifier verify-artifact \
--provenance-path dataslots.intoto.jsonl \
--source-uri github.com/starhel/dataslots \
--source-tag v${VER} \
${PATH_TO_PACKAGE}
```
`VER` is version of package download from PYPI or GH release. Provenance is only available in GH release as PYPI
does not accept jsonl files.
## More about \_\_slots__
* https://docs.python.org/3/reference/datamodel.html#slots
* https://github.com/ericvsmith/dataclasses/issues/28
[dataclasses_issue]: https://github.com/ericvsmith/dataclasses/issues/28
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"description": "# dataslots\n[](https://pypi.org/project/dataslots/)\n[](https://pypi.org/project/dataslots/)\n\n[](https://github.com/starhel/dataslots/actions)\n[](https://github.com/starhel/dataslots/actions)\n\n[](https://slsa.dev)\n\n## Decorator for adding __slots__\nIn python 3.7 dataclasses module was introduced for faster class creation ([PEP 557](https://www.python.org/dev/peps/pep-0557/)).\nUnfortunately, there's no support for `__slots__` (basic support was added in 3.10). If you want to create more memory \nefficient instances, you need to do it by yourself or use `@dataslots` decorator.\n\n## Usage\n### Simple example\n```python\n@dataslots\n@dataclass\nclass Point2D:\n x: int\n y: int\n```\n### Inheritance\nAs described in docs, in derived class `__dict__` is created, because base class does not have `__slots__`. \nSlots are created from all defined properties (returned by `dataclasses.fields()` function).\n```python\n@dataclass\nclass Base:\n a: int\n\n\n@dataslots\n@dataclass\nclass Derived(Base):\n c: int\n d: int\n```\n\n### Dynamic assignment of new variables\n```python\n@dataslots(add_dict=True)\n@dataclass\nclass Point2D:\n x: int\n y: int\n \npoint = Point2D(10, 20)\npoint.length = math.sqrt(point.x ** 2 + point.y ** 2)\n```\n\n### Weakref\n```python\n@dataslots(add_weakref=True)\n@dataclass\nclass Point2D:\n x: int\n y: int\n \npoint = Point2D(10, 20)\nr = weakref.ref(point)\n```\n\n### Read-only class variables\nWith `__slots__` it's possible to define read-only class variables. When using dataclasses you cannot provide type \nfor attribute or use `typing.ClassVar` to declare one. \n```python\n@dataslots\n@dataclass\nclass A:\n x = 5\n y: ClassVar[set] = set()\n```\n\n### Pickling frozen dataclass\nBecause of an [issue 36424](https://bugs.python.org/issue36424) you need custom `__setstate__` method. In dataslots \nthere is implemented default version, and it is used if decorated class has no `__getstate__` and `__setstate__` \nfunction declared.\n\n_Added in 1.0.2_\n\n### Data descriptors\n[Data descriptors](https://docs.python.org/3.7/howto/descriptor.html#descriptor-protocol) are supported by \ninheritance from `DataDescriptor` (base class with required interface) or `DataslotsDescriptor` (class with \nadditional features to simplify descriptor definition). \n\nCheck example directory for basic usage. \n\n_Added in 1.1.0_\n\n### Typing support (PEP 561)\nThe package is PEP 561 compliant, so you can easily use it with mypy<sup>1</sup> and pyright.\n\n<sup>1</sup> Due to some issues in mypy not all features are supported correctly (like [dataclass alike \ninterface](https://github.com/python/mypy/issues/14293) or [descriptors](https://github.com/python/mypy/issues/13856)). \n\n_Added in 1.2.0_\n\n### Backport\nIf you prefer using the newest `dataclasses.dataclass` interface you can use `dataslots.dataclass` wrapper \nto provide a consistent interface regardless of the python version.\n\nNotice: Wrapper always uses `dataslots` to make all additional features available and `slots=True` is obligatory. \n\n_Added in 1.2.0_\n\n## SLSA support\nAll packages from version 1.2.0 can be verified using [SLSA provenance](https://slsa.dev/provenance/v0.2) \n(dataslots package is compliant with [SLSA Level 3](https://slsa.dev/spec/v0.1/levels)).\n\nIf you want to verify dataslots before installing, you need to download \n[SLSA verifier](https://github.com/slsa-framework/slsa-verifier) and run:\n```bash\nslsa-verifier verify-artifact \\\n--provenance-path dataslots.intoto.jsonl \\\n--source-uri github.com/starhel/dataslots \\\n--source-tag v${VER} \\\n${PATH_TO_PACKAGE}\n```\n\n`VER` is version of package download from PYPI or GH release. Provenance is only available in GH release as PYPI\ndoes not accept jsonl files. \n\n## More about \\_\\_slots__\n* https://docs.python.org/3/reference/datamodel.html#slots\n* https://github.com/ericvsmith/dataclasses/issues/28\n\n[dataclasses_issue]: https://github.com/ericvsmith/dataclasses/issues/28\n",
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