strcs 0.5.0

Wrapper to make it more convenient to make structure hooks for cattrs

A Python3.13+ library that wraps cattrs for a modular approach to constructing objects with the ability to string data through the process.

Install from pypi:

> python -m pip install strcs

Documentation at https://strcs.readthedocs.io/

Example

from typing import Annotated, NewType

import attrs

import strcs

reg = strcs.CreateRegister()
creator = reg.make_decorator()

Number = NewType("Number", int)
Word = NewType("Word", str)


@attrs.define(frozen=True)
class Maths(strcs.MetaAnnotation):
    multiply: int

    def calculate(self, val: int) -> Number:
        return Number(val * self.multiply)


class Thing:
    pass


@attrs.define
class Config:
    thing: Annotated[Thing, strcs.FromMeta("thing")]
    words: list[Word]
    some_number: Annotated[Number, Maths(multiply=2)]
    contrived1: str
    contrived2: str
    some_other_number: int = 16


@creator(Number)
def create_number(val: object, /, annotation: Maths) -> strcs.ConvertResponse[Number]:
    if not isinstance(val, int):
        return None

    return annotation.calculate(val)


@creator(Word)
def create_word(val: object, /, word_prefix: str = "") -> strcs.ConvertResponse[Word]:
    if not isinstance(val, str):
        return None

    return Word(f"{word_prefix}{val}")


@creator(Config)
def create_config(val: object, /) -> strcs.ConvertResponse[Config]:
    if not isinstance(val, dict):
        return None

    result = dict(val)
    if "contrived" in result:
        contrived = result.pop("contrived")
        result["contrived1"], result["contrived2"] = contrived.split("_")

    return result


thing = Thing()
meta = strcs.Meta({"thing": thing, "word_prefix": "the_prefix__"})

config = reg.create(
    Config,
    {"words": ["one", "two"], "some_number": 20, "contrived": "stephen_bob"},
    meta=meta,
)
print(config)
assert isinstance(config, Config)
assert config.thing is thing
assert config.words == ["the_prefix__one", "the_prefix__two"]
assert config.some_number == 40
assert config.some_other_number == 16
assert config.contrived1 == "stephen"
assert config.contrived2 == "bob"

Development

To have a virtualenv that has everything needed in it:

> source run.sh activate

To run tests, linting, formatting, type checking:

> ./test.sh
> ./lint
> ./format
> ./types