diff options
Diffstat (limited to 'ext/pybind11/docs/advanced/pycpp')
-rw-r--r-- | ext/pybind11/docs/advanced/pycpp/numpy.rst | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/ext/pybind11/docs/advanced/pycpp/numpy.rst b/ext/pybind11/docs/advanced/pycpp/numpy.rst index 98b0c25b9..458f99e97 100644 --- a/ext/pybind11/docs/advanced/pycpp/numpy.rst +++ b/ext/pybind11/docs/advanced/pycpp/numpy.rst @@ -41,7 +41,7 @@ completely avoid copy operations with Python expressions like py::format_descriptor<float>::format(), /* Python struct-style format descriptor */ 2, /* Number of dimensions */ { m.rows(), m.cols() }, /* Buffer dimensions */ - { sizeof(float) * m.rows(), /* Strides (in bytes) for each index */ + { sizeof(float) * m.cols(), /* Strides (in bytes) for each index */ sizeof(float) } ); }); @@ -261,7 +261,7 @@ simply using ``vectorize``). namespace py = pybind11; py::array_t<double> add_arrays(py::array_t<double> input1, py::array_t<double> input2) { - auto buf1 = input1.request(), buf2 = input2.request(); + py::buffer_info buf1 = input1.request(), buf2 = input2.request(); if (buf1.ndim != 1 || buf2.ndim != 1) throw std::runtime_error("Number of dimensions must be one"); @@ -272,7 +272,7 @@ simply using ``vectorize``). /* No pointer is passed, so NumPy will allocate the buffer */ auto result = py::array_t<double>(buf1.size); - auto buf3 = result.request(); + py::buffer_info buf3 = result.request(); double *ptr1 = (double *) buf1.ptr, *ptr2 = (double *) buf2.ptr, @@ -364,3 +364,23 @@ uses of ``py::array``: The file :file:`tests/test_numpy_array.cpp` contains additional examples demonstrating the use of this feature. + +Ellipsis +======== + +Python 3 provides a convenient ``...`` ellipsis notation that is often used to +slice multidimensional arrays. For instance, the following snippet extracts the +middle dimensions of a tensor with the first and last index set to zero. + +.. code-block:: python + + a = # a NumPy array + b = a[0, ..., 0] + +The function ``py::ellipsis()`` function can be used to perform the same +operation on the C++ side: + +.. code-block:: cpp + + py::array a = /* A NumPy array */; + py::array b = a[py::make_tuple(0, py::ellipsis(), 0)]; |