Handling errors

Everything Thresher rejects raises a subclass of ThresherError, so you can catch this package's failures without also catching unrelated ones from numpy, pandas or your own code:

from thresher import Thresher
from thresher.exceptions import InvalidInputError

try:
    threshold = Thresher().optimize_threshold(scores, actual_classes)
except InvalidInputError as exc:
    print(f"the data cannot be optimized over: {exc}")

The hierarchy

ThresherError
├── ConfigurationError        a name that does not exist            (ValueError)
│   ├── UnknownAlgorithmError
│   └── UnknownBackendError
├── InvalidInputError         the data cannot be optimized over     (ValueError)
│   ├── EmptyInputError
│   ├── UndefinedScoresError
│   ├── LengthMismatchError
│   ├── MissingLabelsError
│   ├── UnexpectedLabelsError
│   ├── SingleClassError
│   └── InsufficientDataError
├── LabelMappingError         the `labels` option cannot map        (TypeError)
├── NotIterableError          scores or classes are not iterable    (AttributeError)
├── BackendDependencyError    an optional dependency is missing     (ImportError)
├── ParallelBootstrapError    worker processes could not start      (RuntimeError)
├── AlgorithmNotWiredError    a bug in this package                 (NotImplementedError)
└── ShardMergeError           a bug in this package                 (ValueError)

Each class also inherits the builtin shown on the right, so except ValueError code keeps working unchanged.

Errors carry their detail

You do not have to parse the message:

from thresher.exceptions import LengthMismatchError, UnknownAlgorithmError

try:
    ...
except LengthMismatchError as exc:
    print(f"{exc.score_count} scores against {exc.class_count} classes")
except UnknownAlgorithmError as exc:
    print(f"{exc.name!r} is not one of {exc.available}")

Exception	Attributes
LengthMismatchError	score_count, class_count
MissingLabelsError	count
UnknownAlgorithmError	name, available
UnknownBackendError	name, available
UnexpectedLabelsError	unexpected
SingleClassError	only

See the API reference for every class.