{"record":{"id":"0f084297ba630691","repo":"microsoft/qlib","slug":"subclass-of-calendarstorage-must-implement-len","errorCode":null,"errorMessage":"Subclass of CalendarStorage must implement `__len__`  method","messagePattern":"Subclass of CalendarStorage must implement `__len__`  method","errorType":"exception","errorClass":"NotImplementedError","httpStatus":null,"severity":"error","filePath":"qlib/data/storage/storage.py","lineNumber":188,"sourceCode":"        ------\n        ValueError\n            If the data(storage) does not exist, raise ValueError\n\n        \"\"\"\n        raise NotImplementedError(\n            \"Subclass of CalendarStorage must implement `__getitem__(i: int)`/`__getitem__(s: slice)`  method\"\n        )\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 CalendarStorage must implement `__len__`  method\")\n\n\nclass InstrumentStorage(BaseStorage):\n    def __init__(self, market: str, freq: str, **kwargs):\n        self.market = market\n        self.freq = freq\n        self.kwargs = kwargs\n\n    @property\n    def data(self) -> Dict[InstKT, InstVT]:\n        \"\"\"get all data\n\n        Raises\n        ------\n        ValueError\n            If the data(storage) does not exist, raise ValueError\n        \"\"\"\n        raise NotImplementedError(\"Subclass of InstrumentStorage must implement `data` method\")","sourceCodeStart":170,"sourceCodeEnd":206,"githubUrl":"https://github.com/microsoft/qlib/blob/79633dd9506ea689e5400dea0197717b5b3d74b7/qlib/data/storage/storage.py#L170-L206","documentation":"Error \"Subclass of CalendarStorage must implement `__len__`  method\" thrown in microsoft/qlib.","triggerScenarios":"This error is raised at qlib/data/storage/storage.py:188 when the guard condition fails: \"Subclass of CalendarStorage 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 CalendarStorage subclass.","Use the built-in FileCalendarStorage 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":"2026-08-15T22:17:37.221Z"}