Add mpz.__array__() method to interact with numpy

Closes #507

pyproject.toml

@@ -39,7 +39,8 @@ content-type = 'text/x-rst'
 
 [project.optional-dependencies]
 docs = ['sphinx>=4', 'sphinx-rtd-theme>=1']
-tests = ['pytest', 'hypothesis', 'cython', 'mpmath', 'setuptools']
+tests = ['pytest', 'hypothesis', 'cython', 'mpmath', 'setuptools',
+         'numpy; python_version>="3.10" and platform_system!="Windows"']
 
 [project.urls]
 Homepage = 'https://github.com/aleaxit/gmpy'

src/gmpy2_mpz.c

@@ -91,6 +91,7 @@ static PyMethodDef GMPy_MPZ_methods[] = {
     { "__round__", (PyCFunction)GMPy_MPZ_Method_Round, METH_FASTCALL, GMPy_doc_mpz_method_round },
     { "__sizeof__", GMPy_MPZ_Method_SizeOf, METH_NOARGS, GMPy_doc_mpz_method_sizeof },
     { "__trunc__", GMPy_MPZ_Method_Trunc, METH_NOARGS, GMPy_doc_mpz_method_trunc },
+    { "__array__", (PyCFunction)GMPy_MPZ_Method_Array, METH_FASTCALL | METH_KEYWORDS, GMPy_doc_mpz_method_array },
     { "bit_clear", GMPy_MPZ_bit_clear_method, METH_O, doc_bit_clear_method },
     { "bit_count", GMPy_MPZ_bit_count_method, METH_NOARGS, doc_bit_count_method },
     { "bit_flip", GMPy_MPZ_bit_flip_method, METH_O, doc_bit_flip_method },

src/gmpy2_mpz_misc.c

@@ -2167,3 +2167,88 @@ GMPy_MP_Method_Conjugate(PyObject *self, PyObject *args)
     Py_INCREF((PyObject*)self);
     return (PyObject*)self;
 }
+
+PyDoc_STRVAR(GMPy_doc_mpz_method_array,
+"x.__array__(dtype=None, copy=None)\n");
+
+static PyObject *
+GMPy_MPZ_Method_Array(PyObject *self, PyObject *const *args,
+                      Py_ssize_t nargs, PyObject *kwnames)
+{
+    Py_ssize_t i, nkws = 0;
+    int argidx[2] = {-1, -1};
+    const char* kwname;
+    PyObject *dtype = Py_None, *copy = Py_None;
+
+    if (nargs > 2) {
+        TYPE_ERROR("__array__() takes at most 2 positional arguments");
+        return NULL;
+    }
+    if (nargs >= 1) {
+        argidx[0] = 0;
+    }
+    if (nargs == 2) {
+        argidx[1] = 1;
+    }
+
+    if (kwnames) {
+        nkws = PyTuple_GET_SIZE(kwnames);
+    }
+    if (nkws > 2) {
+        TYPE_ERROR("__array__() takes at most 2 keyword arguments");
+        return NULL;
+    }
+    for (i = 0; i < nkws; i++) {
+        kwname = PyUnicode_AsUTF8(PyTuple_GET_ITEM(kwnames, i));
+        if (strcmp(kwname, "dtype") == 0) {
+            if (nargs == 0) {
+                argidx[0] = (int)(nargs + i);
+            }
+            else {
+                TYPE_ERROR("argument for __array__() given by name ('dtype') and position (1)");
+                return NULL;
+            }
+        }
+        else if (strcmp(kwname, "copy") == 0) {
+            if (nargs <= 1) {
+                argidx[1] = (int)(nargs + i);
+            }
+            else {
+                TYPE_ERROR("argument for __array__() given by name ('copy') and position (2)");
+                return NULL;
+            }
+        }
+        else {
+            TYPE_ERROR("got an invalid keyword argument for __array__()");
+            return NULL;
+        }
+    }
+
+    if (argidx[0] >= 0) {
+        dtype = args[argidx[0]];
+    }
+    if (argidx[1] >= 0) {
+        copy = args[argidx[1]];
+    }
+
+    PyObject *mod = PyImport_ImportModule("numpy");
+
+    if (!mod) {
+        return NULL;
+    }
+
+    PyObject *tmp_long = GMPy_PyLong_From_MPZ((MPZ_Object *)self, NULL);
+
+    if (!tmp_long) {
+        Py_DECREF(mod);
+        return NULL;
+    }
+
+    PyObject *result = PyObject_CallMethod(mod, "array",
+                                           "OO", tmp_long, dtype);
+
+    Py_DECREF(mod);
+    Py_DECREF(tmp_long);
+
+    return result;
+}

src/gmpy2_mpz_misc.h

@@ -59,6 +59,7 @@ static PyObject * GMPy_MPZ_Method_IsProbabPrime(PyObject *self, PyObject *const
 static PyObject * GMPy_MPZ_Method_IsEven(PyObject *self, PyObject *other);
 static PyObject * GMPy_MPZ_Method_IsOdd(PyObject *self, PyObject *other);
 static PyObject * GMPy_MP_Method_Conjugate(PyObject *self, PyObject *args);
+static PyObject * GMPy_MPZ_Method_Array(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames);
 
 static PyObject * GMPy_MPZ_Function_NumDigits(PyObject *self, PyObject *const *args, Py_ssize_t nargs);
 static PyObject * GMPy_MPZ_Function_Iroot(PyObject *self, PyObject *const *args, Py_ssize_t nargs);

test/test_mpz.py

@@ -3,6 +3,7 @@
 import pickle
 from fractions import Fraction
 
+import pytest
 from hypothesis import assume, example, given, settings
 from hypothesis.strategies import booleans, integers, sampled_from
 from pytest import mark, raises
@@ -1758,3 +1759,17 @@ def test_issue_312():
     assert not is_prime(1 - 2**4423)
     assert all(not is_prime(-a) for a in range(8))
     assert next_prime(-8) == 2
+
+
+def test_mpz_array():
+    numpy = pytest.importorskip('numpy')
+    i = 5579686107214117131790972086716881
+    m = gmpy2.mpz(i)
+    assert numpy.longdouble(m) == numpy.longdouble(i)
+    assert m.__array__(dtype=numpy.longdouble) == numpy.longdouble(i)
+
+    raises(TypeError, lambda: m.__array__(1, 2, 3))
+    raises(TypeError, lambda: m.__array__(dtype=None, copy=None, spam=123))
+    raises(TypeError, lambda: m.__array__(int, dtype=None))
+    raises(TypeError, lambda: m.__array__(int, None, copy=None))
+    raises(TypeError, lambda: m.__array__(spam=123))