typedattr

Deprecated:

Attribute parsing capabilities have been moved to typedparser
Other utilities have been moved to packg
This code and pypi package may be deleted at some point.

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

Note: 0.2 breaks some backwards compatibility. Use 0.1 or update your code.

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 and list)
Supports positional and keyword arguments in classes
Can also typecheck existing attrs instances
Allows custom conversions, by default converts source type str to target type Path and int to float
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.

Other utilities in the package

Const: An alternative to enum.Enum for defining constants
cacheutils: Cache objects to disk / to memory
objutils: Various utilities like nested modification of dicts
Type definitions and other utilities

Install locally and run tests

Clone repository and cd into, then:

pip install -e .
pip install -U 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.

simon-ging/typedattr