SafeModel

A safe container, a wrapper around a structure whose schema is unknown or may dynamically change.

The idea is to put an object (e.g. a structure that is retrieved from an external source) in a container that will support the __getattr__ and __getitem__ methods, but will not throw errors if non-existent data is accessed.

How to install

Using uv

uv add safemodel

Using pip

pip install safemodel

How to Use

General

SafeModel is a potentially iterable object. If we try to iterate it, we get: 1. If iterable is wrapped: (SafeModel(x) for x in iterable) 2. If non-iterable is wrapped: empty iterator

When unpacking a wraparound value via __call__, it is passed to each processor sequentially. If any processor raises ProcessingError, the value will be replaced with Placeholder. If there is no wraparound data, Placeholder will be returned.

Processors

Functions that take 1 positional argument and return a value (usually the one passed in unchanged, but it can be changed) or throw a ProcessingError exception. The result of a processor is used by the next one in the chain.

NO_DATA

A special value denoting the absence of data. None is not suitable because it may be the expected value in some cases. The object denoting the absence of data must be fundamentally unobtainable from the source structure.

Examples

from safemodel import SafeModel, default_placeholder_context


unsafe_struct = {
    "hello": "world",
    "list_of_optional_dict_with_value": [
        {"value": 1},
        None,
        {"value": 2},
        3,
        4,
    ],
    "age_str": "24",
    "strange_struct": {
        "foo": "bar",
        "members": [
            {
                "fio": {
                    "name": "Ivan",
                }
            },
        ],
    },
    "camelCaseField": "ok",
}

safe_struct = SafeModel(unsafe_struct)

assert safe_struct.hello() == "world"

expected_values = [1, "-", 2, "-", "-"]
actual_values_1 = [value_container.value("-") for value_container in safe_struct.list_of_optional_dict_with_value]

with default_placeholder_context(safe_struct, "-"):
    actual_values_2 = [value_container.value() for value_container in safe_struct.list_of_optional_dict_with_value]

assert actual_values_1 == actual_values_2 == expected_values

assert safe_struct.age_str | int == 24

assert safe_struct.camel_case_field() == "ok"

assert safe_struct.strange_struct.members[0].fio.name() == "Ivan"

assert safe_struct.some.field.that.does.not_.exist("Nothing!!!") == "Nothing!!!"
assert not safe_struct.some.field.that.does.not_.exist.should.be.false

assert safe_struct.age_str | [float, str] == safe_struct.age_str(extend_processors=[float, str]) == "24.0"

How To Develop

Prepare your environment (once)

Install uv

Using scoop

scoop install uv

Without scoop

powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"

Run Linter

Using Make

make lintfix

If Make is not installed

uv run ruff format
uv run ruff check --fix

Run Tests

With Make

make

or

make test

Without Make

uv pip install -e .
uv run pytest -v

Build

uv build