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prefect.events.schemas.labelling

LabelDiver

The LabelDiver supports templating use cases for any Labelled object, by presenting the labels as a graph of objects that may be accessed by attribute. For example:

diver = LabelDiver({
    'hello.world': 'foo',
    'hello.world.again': 'bar'
})

assert str(diver.hello.world) == 'foo'
assert str(diver.hello.world.again) == 'bar'
Source code in src/prefect/events/schemas/labelling.py
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class LabelDiver:
    """The LabelDiver supports templating use cases for any Labelled object, by
    presenting the labels as a graph of objects that may be accessed by attribute.  For
    example:

        diver = LabelDiver({
            'hello.world': 'foo',
            'hello.world.again': 'bar'
        })

        assert str(diver.hello.world) == 'foo'
        assert str(diver.hello.world.again) == 'bar'

    """

    _value: str
    _divers: Dict[str, "LabelDiver"]
    _labels: Dict[str, str]

    def __init__(self, labels: Dict[str, str], value: str = ""):
        self._labels = labels.copy()
        self._value = value

        divers: Dict[str, Dict[str, str]] = {}
        values: Dict[str, str] = {}

        for key, value in labels.items():
            head, _, tail = key.partition(".")
            if tail:
                if head not in divers:
                    divers[head] = {}

                divers[head][tail] = labels[key]
            else:
                values[head] = value

        # start with keys that had sub-divers...
        self._divers: Dict[str, LabelDiver] = {
            k: LabelDiver(v, value=values.pop(k, "")) for k, v in divers.items()
        }
        # ...then mix in any remaining keys that _only_ had values
        self._divers.update(**{k: LabelDiver({}, value=v) for k, v in values.items()})

    def __str__(self) -> str:
        return self._value or ""

    def __repr__(self) -> str:
        return f"LabelDiver(divers={self._divers!r}, value={self._value!r})"

    def __len__(self) -> int:
        return len(self._labels)

    def __iter__(self) -> Iterator[Tuple[str, str]]:
        return iter(self._labels.items())

    def __getitem__(self, key: str) -> str:
        return self._labels[key]

    def __getattr__(self, name: str) -> "LabelDiver":
        if name.startswith("_"):
            raise AttributeError

        try:
            return self._divers[name]
        except KeyError:
            raise AttributeError