René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Support for custom types?","articleBody":"I'm trying to wrap a custom type using pybind11 and xtensor-python. Although I can create a numpy array of my wrapped type from Python, I cannot pass this numpy array to C++ functions or pass xt::xarray to Python.\r\n\r\nThe C++ part is\r\n\r\n```c++\r\n#include \u003cpybind11/numpy.h\u003e\r\n#include \u003cpybind11/pybind11.h\u003e\r\n\r\n#include \u003cxtensor/xarray.hpp\u003e\r\n#define FORCE_IMPORT_ARRAY\r\n#include \u003cxtensor-python/pyarray.hpp\u003e\r\n\r\nstruct Quantity\r\n{\r\n    double q;\r\n    \r\n    Quantity(double q=0)\r\n    : q(q)\r\n    {\r\n    }\r\n};\r\n\r\nPYBIND11_MODULE(test_array, test_array)\r\n{\r\n    xt::import_numpy();\r\n    \r\n    pybind11::class_\u003cQuantity\u003e(test_array, \"Quantity\")\r\n        .def(pybind11::init\u003cdouble\u003e())\r\n        .def_readwrite(\"q\", \u0026Quantity::q);\r\n    \r\n    test_array.def(\"create\", []() { return xt::xarray\u003cQuantity\u003e{1.1, 2.2}; });\r\n    test_array.def(\r\n        \"consume\", [](xt::xarray\u003cQuantity\u003e const \u0026 array) {\r\n            for(auto \u0026\u0026 item: array)\r\n            {\r\n                std::cout \u003c\u003c item.q \u003c\u003c \"\\n\";\r\n            }\r\n        });\r\n}\r\n```\r\n\r\nAnd the Python code\r\n```python\r\nimport numpy\r\nimport test_array\r\n\r\nq1 = test_array.Quantity(42)\r\nq2 = test_array.Quantity(3.14)\r\na = numpy.array([q1, q2])\r\n\r\nprint([x.q for x in a])\r\n\r\ntry:\r\n    test_array.create()\r\nexcept Exception as e:\r\n    print(e)\r\n\r\ntry:\r\n    test_array.consume(a)\r\nexcept Exception as e:\r\n    print(e)\r\n```\r\n\r\nBoth try/except blocks in Python yield a RuntimeError saying \"NumPy type info missing for 8Quantity\"\r\n\r\nIs this use case supported by xtensor-python? If so, what am I missing? If not, what alternative would you suggest?","author":{"url":"https://github.com/lamyj","@type":"Person","name":"lamyj"},"datePublished":"2022-12-17T14:59:28.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/285/xtensor-python/issues/285"}