Typed conversion of dictionaries to attrs instances
Project description
typedattr
Typechecking and conversion utility for attrs
Parses a dictionary into an attrs instance. Contains other generic object, type and cache utilities.
Install
Requires python>=3.7
pip install typedattr
Quickstart
Define the class hierarchy and parse the input using attrs_from_dict
:
from attrs import define
from typing import Optional
from typedattr import attrs_from_dict
@define
class Cfg:
foo: int = 12
bar: Optional[int] = None
print(attrs_from_dict(Cfg, {"foo": 1, "bar": 2}))
# Cfg(foo=1, bar=2)
@define
class CfgNested:
sub_cfg: Cfg = None
print(attrs_from_dict(CfgNested, {"sub_cfg": {"foo": 1, "bar": 2}}))
# CfgNested(sub_cfg=Cfg(foo=1, bar=2))
Features
- Nested checking and conversion of python standard types
- Supports old and new style typing (e.g.
typing.List
andlist
) - Supports positional and keyword arguments in classes
- Can also typecheck existing attrs instances
- Allows custom conversions, by default converts source type
str
to target typePath
andint
tofloat
- Allows to redefine which objects will be recursed into, by default recurses into standard containers (list, dict, etc.)
@definenumpy
decorator for equality check if the instances contains numpy arrays
Strict mode (default)
- Convert everything to the target type, e.g. if the input is a list and the annotation is a tuple, the output will be a tuple
- Raise errors if types cannot be matched, there are unknown fields in the input or abstract annotation types are used (e.g. Sequence)
Non-strict mode
Enabled by calling attrs_from_dict
with strict=False
- No conversion except for creating the attrs instance from the dict
- Ignore silently if types cannot be matched or abstract annotation types are used
- Unknown fields in the input will be added to the attrs instance if possible (see the hint below about slots)
Skip unknowns
Set skip_unknowns=True
to ignore all unknown input fields.
Hints
The following behaviour stems from the attrs
package:
- New attributes cannot to be added after class definition to an attrs instance,
unless it is created with
@define(slots=False)
Explanation - Untyped fields or "ClassVar" typed fields will be ignored by @attrs.define and therefore also by this library.
Possible improvements
- Supports Callable but does not typecheck the signature
- Not tested for NewType, Literal
Install locally and run tests
Clone repository and cd into, then:
pip install -e .
pip install pytest pytest-cov pylint
pylint typedattr
# run tests for python>=3.7
python -m pytest --cov
pylint tests
# run tests for python>=3.9
python -m pytest tests tests_py39 --cov
pylint tests
pylint tests_py39
Alternatives
This library should be useful for off-the-shelf typechecking and conversion of dicts to attrs instances.
For more complex or other related use cases there are many alternatives:
cattrs
, attrs-strict
, pydantic
, dataconf
, omegaconf
to name a few.
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