How to determine if a PyObject is a numpy PyArrayObject

Question

I'm new to the Python C-API.

Currently I get objects from the embedded Python module via

PyObject* a = (PyObject*) PyObject_GetAttrString(pModule, "a");
std::cout << "a as long is " << PyLong_AsLong(a) << std::endl;

I access numpy objects via

PyArrayObject* array = (PyArrayObject*) PyObject_GetAttrString(pModule, "A");

How can I test if the object is a really a PyArrayObject? In other words how to do what I would do in Python via isinstance(a, numpy.ndarray)?

Warren Weckesser · Accepted Answer · 2020-10-09 20:48:24Z

7

Use PyArray_Check or PyArray_CheckExact. Use PyArray_Check if subclasses are okay, or PyArray_CheckExact if you need an object with type exactly numpy.ndarray.

edited Oct 9, 2020 at 20:48

answered Oct 9, 2020 at 20:40

Warren Weckesser

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3 Comments

Fabian Over a year ago

This does not work for me ?! But I need to note, that I'm also not able to allocate a numpy array from C++ side (same code on macOS with clang and Linux with gcc 10). std::cout << "check a: " << PyArray_Check(a) << std::endl; results in

isinstance : unknown location:0: fatal error: in embedded_python: memory access violation at address: 0x00000010: no mapping at fault address

Fabian Over a year ago

I made a mistake pasting my error: It is

check a: unknown location:0: fatal error: in   "embedded_python": memory access violation at   address: 0x00000010: no mapping at fault address

- both solutions fail for me?!

Warren Weckesser Over a year ago

That sounds like a new question. Instead of trying to figure that out here in the comments, create a new question about the error.

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