Merge pull request #440 from wjakob/master

Permit creation of NumPy arrays with a "base" object that owns the data

include/pybind11/common.h

@@ -455,6 +455,7 @@ PYBIND11_RUNTIME_EXCEPTION(stop_iteration, PyExc_StopIteration)
 PYBIND11_RUNTIME_EXCEPTION(index_error, PyExc_IndexError)
 PYBIND11_RUNTIME_EXCEPTION(key_error, PyExc_KeyError)
 PYBIND11_RUNTIME_EXCEPTION(value_error, PyExc_ValueError)
+PYBIND11_RUNTIME_EXCEPTION(import_error, PyExc_ImportError)
 PYBIND11_RUNTIME_EXCEPTION(type_error, PyExc_TypeError)
 PYBIND11_RUNTIME_EXCEPTION(cast_error, PyExc_RuntimeError) /// Thrown when pybind11::cast or handle::call fail due to a type casting error
 PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used internally

include/pybind11/numpy.h

@@ -22,8 +22,8 @@
 #include <functional>
 
 #if defined(_MSC_VER)
-#pragma warning(push)
-#pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
+#  pragma warning(push)
+#  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
 #endif
 
 /* This will be true on all flat address space platforms and allows us to reduce the
@@ -156,8 +156,10 @@ NAMESPACE_END(detail)
     (reinterpret_cast<::pybind11::detail::PyArray_Proxy*>(ptr)->attr)
 #define PyArrayDescr_GET_(ptr, attr) \
     (reinterpret_cast<::pybind11::detail::PyArrayDescr_Proxy*>(ptr)->attr)
+#define PyArray_FLAGS_(ptr) \
+    PyArray_GET_(ptr, flags)
 #define PyArray_CHKFLAGS_(ptr, flag) \
-    (flag == (reinterpret_cast<::pybind11::detail::PyArray_Proxy*>(ptr)->flags & flag))
+    (flag == (PyArray_FLAGS_(ptr) & flag))
 
 class dtype : public object {
 public:
@@ -258,38 +260,62 @@ public:
         forcecast = detail::npy_api::NPY_ARRAY_FORCECAST_
     };
 
-    array(const pybind11::dtype& dt, const std::vector<size_t>& shape,
-          const std::vector<size_t>& strides, const void *ptr = nullptr) {
+    array(const pybind11::dtype &dt, const std::vector<size_t> &shape,
+          const std::vector<size_t> &strides, const void *ptr = nullptr,
+          handle base = handle()) {
         auto& api = detail::npy_api::get();
         auto ndim = shape.size();
         if (shape.size() != strides.size())
             pybind11_fail("NumPy: shape ndim doesn't match strides ndim");
         auto descr = dt;
+
+        int flags = 0;
+        if (base && ptr) {
+            array base_array(base, true);
+            if (base_array.check())
+                /* Copy flags from base (except baseship bit) */
+                flags = base_array.flags() & ~detail::npy_api::NPY_ARRAY_OWNDATA_;
+            else
+                /* Writable by default, easy to downgrade later on if needed */
+                flags = detail::npy_api::NPY_ARRAY_WRITEABLE_;
+        }
+
         object tmp(api.PyArray_NewFromDescr_(
             api.PyArray_Type_, descr.release().ptr(), (int) ndim, (Py_intptr_t *) shape.data(),
-            (Py_intptr_t *) strides.data(), const_cast<void *>(ptr), 0, nullptr), false);
+            (Py_intptr_t *) strides.data(), const_cast<void *>(ptr), flags, nullptr), false);
         if (!tmp)
             pybind11_fail("NumPy: unable to create array!");
-        if (ptr)
-            tmp = object(api.PyArray_NewCopy_(tmp.ptr(), -1 /* any order */), false);
+        if (ptr) {
+            if (base) {
+                PyArray_GET_(tmp.ptr(), base) = base.inc_ref().ptr();
+            } else {
+                tmp = object(api.PyArray_NewCopy_(tmp.ptr(), -1 /* any order */), false);
+            }
+        }
         m_ptr = tmp.release().ptr();
     }
 
-    array(const pybind11::dtype& dt, const std::vector<size_t>& shape, const void *ptr = nullptr)
-    : array(dt, shape, default_strides(shape, dt.itemsize()), ptr) { }
+    array(const pybind11::dtype &dt, const std::vector<size_t> &shape,
+          const void *ptr = nullptr, handle base = handle())
+        : array(dt, shape, default_strides(shape, dt.itemsize()), ptr, base) { }
 
-    array(const pybind11::dtype& dt, size_t count, const void *ptr = nullptr)
-    : array(dt, std::vector<size_t> { count }, ptr) { }
+    array(const pybind11::dtype &dt, size_t count, const void *ptr = nullptr,
+          handle base = handle())
+        : array(dt, std::vector<size_t>{ count }, ptr, base) { }
 
     template<typename T> array(const std::vector<size_t>& shape,
-                               const std::vector<size_t>& strides, const T* ptr)
-    : array(pybind11::dtype::of<T>(), shape, strides, (void *) ptr) { }
+                               const std::vector<size_t>& strides,
+                               const T* ptr, handle base = handle())
+    : array(pybind11::dtype::of<T>(), shape, strides, (void *) ptr, base) { }
 
-    template<typename T> array(const std::vector<size_t>& shape, const T* ptr)
-    : array(shape, default_strides(shape, sizeof(T)), ptr) { }
+    template <typename T>
+    array(const std::vector<size_t> &shape, const T *ptr,
+          handle base = handle())
+        : array(shape, default_strides(shape, sizeof(T)), ptr, base) { }
 
-    template<typename T> array(size_t count, const T* ptr)
-    : array(std::vector<size_t> { count }, ptr) { }
+    template <typename T>
+    array(size_t count, const T *ptr, handle base = handle())
+        : array(std::vector<size_t>{ count }, ptr, base) { }
 
     array(const buffer_info &info)
     : array(pybind11::dtype(info), info.shape, info.strides, info.ptr) { }
@@ -319,6 +345,11 @@ public:
         return (size_t) PyArray_GET_(m_ptr, nd);
     }
 
+    /// Base object
+    object base() const {
+        return object(PyArray_GET_(m_ptr, base), true);
+    }
+
     /// Dimensions of the array
     const size_t* shape() const {
         return reinterpret_cast<const size_t *>(PyArray_GET_(m_ptr, dimensions));
@@ -343,6 +374,11 @@ public:
         return strides()[dim];
     }
 
+    /// Return the NumPy array flags
+    int flags() const {
+        return PyArray_FLAGS_(m_ptr);
+    }
+
     /// If set, the array is writeable (otherwise the buffer is read-only)
     bool writeable() const {
         return PyArray_CHKFLAGS_(m_ptr, detail::npy_api::NPY_ARRAY_WRITEABLE_);
@@ -436,14 +472,17 @@ public:
 
     array_t(const buffer_info& info) : array(info) { }
 
-    array_t(const std::vector<size_t>& shape, const std::vector<size_t>& strides, const T* ptr = nullptr)
-    : array(shape, strides, ptr) { }
+    array_t(const std::vector<size_t> &shape,
+            const std::vector<size_t> &strides, const T *ptr = nullptr,
+            handle base = handle())
+        : array(shape, strides, ptr, base) { }
 
-    array_t(const std::vector<size_t>& shape, const T* ptr = nullptr)
-    : array(shape, ptr) { }
+    array_t(const std::vector<size_t> &shape, const T *ptr = nullptr,
+            handle base = handle())
+        : array(shape, ptr, base) { }
 
-    array_t(size_t count, const T* ptr = nullptr)
-    : array(count, ptr) { }
+    array_t(size_t count, const T *ptr = nullptr, handle base = handle())
+        : array(count, ptr, base) { }
 
     constexpr size_t itemsize() const {
         return sizeof(T);

include/pybind11/pybind11.h

@@ -567,7 +567,7 @@ public:
     static module import(const char *name) {
         PyObject *obj = PyImport_ImportModule(name);
         if (!obj)
-            pybind11_fail("Module \"" + std::string(name) + "\" not found!");
+            throw import_error("Module \"" + std::string(name) + "\" not found!");
         return module(obj, false);
     }
 };
@@ -1344,15 +1344,27 @@ PYBIND11_NOINLINE inline void print(tuple args, dict kwargs) {
     auto sep = kwargs.contains("sep") ? kwargs["sep"] : cast(" ");
     auto line = sep.attr("join")(strings);
 
-    auto file = kwargs.contains("file") ? kwargs["file"].cast<object>()
-                                        : module::import("sys").attr("stdout");
+    object file;
+    if (kwargs.contains("file")) {
+        file = kwargs["file"].cast<object>();
+    } else {
+        try {
+            file = module::import("sys").attr("stdout");
+        } catch (const import_error &) {
+            /* If print() is called from code that is executed as
+               part of garbage collection during interpreter shutdown,
+               importing 'sys' can fail. Give up rather than crashing the
+               interpreter in this case. */
+            return;
+        }
+    }
+
     auto write = file.attr("write");
     write(line);
     write(kwargs.contains("end") ? kwargs["end"] : cast("\n"));
 
-    if (kwargs.contains("flush") && kwargs["flush"].cast<bool>()) {
+    if (kwargs.contains("flush") && kwargs["flush"].cast<bool>())
         file.attr("flush")();
-    }
 }
 NAMESPACE_END(detail)
 

tests/test_numpy_array.cpp

@@ -99,4 +99,29 @@ test_initializer numpy_array([](py::module &m) {
     sm.def("make_c_array", [] {
         return py::array_t<float>({ 2, 2 }, { 8, 4 });
     });
+
+    sm.def("wrap", [](py::array a) {
+        return py::array(
+            a.dtype(),
+            std::vector<size_t>(a.shape(), a.shape() + a.ndim()),
+            std::vector<size_t>(a.strides(), a.strides() + a.ndim()),
+            a.data(),
+            a
+        );
+    });
+
+    struct ArrayClass {
+        int data[2] = { 1, 2 };
+        ArrayClass() { py::print("ArrayClass()"); }
+        ~ArrayClass() { py::print("~ArrayClass()"); }
+    };
+
+    py::class_<ArrayClass>(sm, "ArrayClass")
+        .def(py::init<>())
+        .def("numpy_view", [](py::object &obj) {
+            py::print("ArrayClass::numpy_view()");
+            ArrayClass &a = obj.cast<ArrayClass&>();
+            return py::array_t<int>({2}, {4}, a.data, obj);
+        }
+    );
 });

tests/test_numpy_array.py

 import pytest
+import gc
 
 with pytest.suppress(ImportError):
     import numpy as np
@@ -149,6 +150,7 @@ def test_bounds_check(arr):
             index_at(arr, 0, 4)
         assert str(excinfo.value) == 'index 4 is out of bounds for axis 1 with size 3'
 
+
 @pytest.requires_numpy
 def test_make_c_f_array():
     from pybind11_tests.array import (
@@ -158,3 +160,81 @@ def test_make_c_f_array():
     assert not make_c_array().flags.f_contiguous
     assert make_f_array().flags.f_contiguous
     assert not make_f_array().flags.c_contiguous
+
+
+@pytest.requires_numpy
+def test_wrap():
+    from pybind11_tests.array import wrap
+
+    def assert_references(A, B):
+        assert A is not B
+        assert A.__array_interface__['data'][0] == \
+               B.__array_interface__['data'][0]
+        assert A.shape == B.shape
+        assert A.strides == B.strides
+        assert A.flags.c_contiguous == B.flags.c_contiguous
+        assert A.flags.f_contiguous == B.flags.f_contiguous
+        assert A.flags.writeable == B.flags.writeable
+        assert A.flags.aligned == B.flags.aligned
+        assert A.flags.updateifcopy == B.flags.updateifcopy
+        assert np.all(A == B)
+        assert not B.flags.owndata
+        assert B.base is A
+        if A.flags.writeable and A.ndim == 2:
+            A[0, 0] = 1234
+            assert B[0, 0] == 1234
+
+    A1 = np.array([1, 2], dtype=np.int16)
+    assert A1.flags.owndata and A1.base is None
+    A2 = wrap(A1)
+    assert_references(A1, A2)
+
+    A1 = np.array([[1, 2], [3, 4]], dtype=np.float32, order='F')
+    assert A1.flags.owndata and A1.base is None
+    A2 = wrap(A1)
+    assert_references(A1, A2)
+
+    A1 = np.array([[1, 2], [3, 4]], dtype=np.float32, order='C')
+    A1.flags.writeable = False
+    A2 = wrap(A1)
+    assert_references(A1, A2)
+
+    A1 = np.random.random((4, 4, 4))
+    A2 = wrap(A1)
+    assert_references(A1, A2)
+
+    A1 = A1.transpose()
+    A2 = wrap(A1)
+    assert_references(A1, A2)
+
+    A1 = A1.diagonal()
+    A2 = wrap(A1)
+    assert_references(A1, A2)
+
+
+@pytest.requires_numpy
+def test_numpy_view(capture):
+    from pybind11_tests.array import ArrayClass
+    with capture:
+        ac = ArrayClass()
+        ac_view_1 = ac.numpy_view()
+        ac_view_2 = ac.numpy_view()
+        assert np.all(ac_view_1 == np.array([1, 2], dtype=np.int32))
+        del ac
+        gc.collect()
+    assert capture == """
+        ArrayClass()
+        ArrayClass::numpy_view()
+        ArrayClass::numpy_view()
+    """
+    ac_view_1[0] = 4
+    ac_view_1[1] = 3
+    assert ac_view_2[0] == 4
+    assert ac_view_2[1] == 3
+    with capture:
+        del ac_view_1
+        del ac_view_2
+        gc.collect()
+    assert capture == """
+        ~ArrayClass()
+    """