{"record":{"id":"e1a3ac3bb635b6a4","repo":"microsoft/qlib","slug":"subclass-of-instrumentstorage-must-implement-le","errorCode":null,"errorMessage":"Subclass of InstrumentStorage must implement `__len__`  method","messagePattern":"Subclass of InstrumentStorage must implement `__len__`  method","errorType":"exception","errorClass":"NotImplementedError","httpStatus":null,"severity":"error","filePath":"qlib/data/storage/storage.py","lineNumber":252,"sourceCode":"        ValueError\n            If the data(storage) does not exist, raise ValueError\n        \"\"\"\n        raise NotImplementedError(\"Subclass of InstrumentStorage must implement `__delitem__` method\")\n\n    def __getitem__(self, k: InstKT) -> InstVT:\n        \"\"\"x.__getitem__(k) <==> x[k]\"\"\"\n        raise NotImplementedError(\"Subclass of InstrumentStorage must implement `__getitem__` method\")\n\n    def __len__(self) -> int:\n        \"\"\"\n\n        Raises\n        ------\n        ValueError\n            If the data(storage) does not exist, raise ValueError\n\n        \"\"\"\n        raise NotImplementedError(\"Subclass of InstrumentStorage must implement `__len__`  method\")\n\n\nclass FeatureStorage(BaseStorage):\n    def __init__(self, instrument: str, field: str, freq: str, **kwargs):\n        self.instrument = instrument\n        self.field = field\n        self.freq = freq\n        self.kwargs = kwargs\n\n    @property\n    def data(self) -> pd.Series:\n        \"\"\"get all data\n\n        Notes\n        ------\n        if data(storage) does not exist, return empty pd.Series: `return pd.Series(dtype=np.float32)`\n        \"\"\"\n        raise NotImplementedError(\"Subclass of FeatureStorage must implement `data` method\")","sourceCodeStart":234,"sourceCodeEnd":270,"githubUrl":"https://github.com/microsoft/qlib/blob/79633dd9506ea689e5400dea0197717b5b3d74b7/qlib/data/storage/storage.py#L234-L270","documentation":"Error \"Subclass of InstrumentStorage must implement `__len__`  method\" thrown in microsoft/qlib.","triggerScenarios":"This error is raised at qlib/data/storage/storage.py:252 when the guard condition fails: \"Subclass of InstrumentStorage must implement `__len__` method\". It triggers when the code path receives input or a state that violates the precondition checked at this point — e.g. an unimplemented abstract method being called, an unsupported argument type/value, or an invalid configuration. To avoid it, satisfy the documented precondition before this call: implement the required method in your subclass, or pass a supported value of the expected type as described by the message.","commonSituations":"See trigger scenarios.","solutions":["Implement the `__len__` method in your InstrumentStorage subclass.","Use the built-in FileInstrumentStorage which implements `__len__`."],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"79633dd9506ea689e5400dea0197717b5b3d74b7","analyzedAt":"2026-08-15T07:01:27.511Z","schemaVersion":2},"datasetVersion":"2026-08-15T17:31:12.345Z"}