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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Weird behavior of casting nd.ndarray on different types","articleBody":"### Environment\r\n\r\n-   Pythonnet version: 3.0.3\r\n-   Python version: 3.12.4\r\n-   Operating System: Windows 11 23H2\r\n-   .NET Runtime: net8.0\r\n-   numpy Version: 2.0.0\r\n\r\n### Details\r\n\r\n-   Describe what you were trying to get done.\r\n\r\n    I am currently migrating from an older undefined pythonnet Version to 3.0.3 with an corresponding upgrade of python from 3.7.9 to 3.12.4.\r\n\r\n    We had some C# logic in place which executed python code and took the result of Tuple[nd.ndarray(dtype=int), nd.ndarray(dtype=float)] and converted it from dynamic to concrete types.\r\n\r\nI am experiencing issues while converting the nd.ndarray(dtype=int) via (long[])result[0]\r\n\r\n\u003e ---- System.Exception : Cannot convert to System.Int64 array\r\n\u003e -------- Microsoft.CSharp.RuntimeBinder.RuntimeBinderException : Cannot convert type 'Python.Runtime.PyObject' to 'long[]'\r\n\r\n\r\nThe nd.ndarray(dtype=float) via (double[])result[1] works as a charme.\r\nSame as when I both return as dtype=float and convert them to double.\r\n\r\nMy current workaround is iterating over the nd.ndarray(dtype=int) with the size of the result array by calling ToArrayByIteration\u003clong\u003e()\r\n\r\nAm I missing something?\r\n\r\n-   What commands did you run to trigger this issue? If you can provide a\r\n    [Minimal, Complete, and Verifiable example](http://stackoverflow.com/help/mcve)\r\n    this will help us understand the issue.\r\n\r\nProblematic here is converting \"indices\" from dtype=int to long in C#. The datatype of the result in C# in Debug view seems to be Int64.\r\n```python\r\n    @staticmethod\r\n    def method(rate: int, data: np.ndarray) -\u003e Tuple[np.ndarray, np.ndarray]:\r\n        ds = int(rate)\r\n        indices = np.arange(len(data), dtype=int)\r\n        result_data = np.array(data, dtype=float)\r\n\r\n        n = len(indices )\r\n        indices = indices [:n * ds:ds]\r\n        result_data = result_data [:n * ds].reshape(n, ds).mean(axis=1)\r\n\r\n        return indices , result_data \r\n```\r\n\r\nReturning dtype=float is not intended but works with the same conversion to double.\r\n```python\r\n    @staticmethod\r\n    def method(rate: int, data: np.ndarray) -\u003e Tuple[np.ndarray, np.ndarray]:\r\n        ds = int(rate)\r\n        indices = np.arange(len(data), dtype=float)\r\n        result_data = np.array(data, dtype=float)\r\n\r\n        n = len(indices )\r\n        indices = indices [:n * ds:ds]\r\n        result_data = result_data [:n * ds].reshape(n, ds).mean(axis=1)\r\n\r\n        return indices , result_data \r\n```\r\n\r\nI left out initialising pythonengine and loading the module in this case.\r\n```csharp\r\npublic class Wrapper \r\n{\r\n    public (long[] x, double[] y) ExecutePythonMethod(\r\n    int rate,\r\n    List\u003cdouble\u003e data)\r\n    {\r\n        using var _ = Py.GIL();\r\n        var result = _module.class.method(rate, data);\r\n\r\n        var x = PythonDataConverter.ToArrayByIteration\u003clong\u003e(result[0]);\r\n        var y = PythonDataConverter.ToArray\u003cdouble\u003e(result[1]);\r\n        return (x, y);\r\n    }\r\n}\r\n\r\npublic static class PythonDataConverter\r\n{\r\n    public static T[] ToArrayByIteration\u003cT\u003e(dynamic arrayFromPython)\r\n    {\r\n        var size = (long)arrayFromPython.size;\r\n\r\n            var array = new T[size];\r\n\r\n            for (var i = 0; i \u003c size; i++)\r\n            {\r\n                array[i] = (T)arrayFromPython[i];\r\n            }\r\n\r\n            return array;\r\n    }\r\n\r\n    public static T[] ToArray\u003cT\u003e(dynamic arrayFromPython)\r\n    {\r\n            return (T[])arrayFromPython;\r\n    }\r\n}\r\n\r\n```","author":{"url":"https://github.com/Trippley","@type":"Person","name":"Trippley"},"datePublished":"2024-07-01T13:22:57.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/2407/pythonnet/issues/2407"}