{"record":{"id":"909b504fccb39ecf","repo":"keras-team/keras","slug":"got-no-xs-to-scan-over-and-length-not-provided","errorCode":null,"errorMessage":"Got no `xs` to scan over and `length` not provided.","messagePattern":"Got no `xs` to scan over and `length` not provided\\.","errorType":"validation","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"keras/src/backend/numpy/core.py","lineNumber":177,"sourceCode":"    def g(_, x):\n        return (), f(x)\n\n    _, ys = scan(g, (), xs)\n    return ys\n\n\ndef scan(f, init, xs=None, length=None, reverse=False, unroll=1):\n    # Ref: jax.lax.scan\n    if not callable(f):\n        raise TypeError(f\"`f` should be a callable. Received: f={f}\")\n    if not isinstance(unroll, bool):\n        if not isinstance(unroll, int) or unroll < 1:\n            raise ValueError(\n                \"`unroll` must be an positive integer or boolean. \"\n                f\"Received: unroll={unroll}\"\n            )\n    if xs is None and length is None:\n        raise ValueError(\"Got no `xs` to scan over and `length` not provided.\")\n\n    input_is_sequence = tree.is_nested(xs)\n    output_is_sequence = tree.is_nested(init)\n\n    def pack_input(x):\n        return tree.pack_sequence_as(xs, x) if input_is_sequence else x[0]\n\n    def pack_output(x):\n        return tree.pack_sequence_as(init, x) if output_is_sequence else x[0]\n\n    if xs is None:\n        xs_flat = []\n        n = int(length)\n    else:\n        xs_flat = tree.flatten(xs)\n        xs_flat = [convert_to_tensor(elem) for elem in xs_flat]\n        n = int(length) if length is not None else shape(xs_flat[0])[0]\n","sourceCodeStart":159,"sourceCodeEnd":195,"githubUrl":"https://github.com/keras-team/keras/blob/7a34a03db60bf60042242d6a556fc3be119046a5/keras/src/backend/numpy/core.py#L159-L195","documentation":"Error \"Got no `xs` to scan over and `length` not provided.\" thrown in keras-team/keras.","triggerScenarios":"Thrown at keras/src/backend/numpy/core.py:177 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":[],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"7a34a03db60bf60042242d6a556fc3be119046a5","analyzedAt":"2026-08-25T21:25:25.994Z","schemaVersion":2},"datasetVersion":"2026-08-26T02:17:13.382Z"}