Expose C++ buffer as Python 3 bytes

Question

Using Boost::Python, is there a way to make a raw C++ buffer accessible to Python 3.2 as a bytes object?

There is a Python 2 answer to a very similar question, but the PyBuffer_FromReadWriteMemory function described there no longer exist in Python 3.

Edit: thanks to user2167433's answer, what I actually want is a read only memoryview object, not a bytes object (using a memoryview avoids copying the buffer I believe).

Why a bytes object? Is the buffer immutable?

user395760
– user395760

2014-04-14 15:46:52 +00:00
Commented Apr 14, 2014 at 15:46 — user395760
– user395760, Commented Apr 14, 2014 at 15:46
@delnan Yes the buffer is immutable.

Rob Agar
– Rob Agar

2014-04-14 15:59:12 +00:00
Commented Apr 14, 2014 at 15:59 — Rob Agar
– Rob Agar, Commented Apr 14, 2014 at 15:59

brookskd · Accepted Answer · 2014-04-14 19:03:53Z

15

Python > 3 and Python <= 3.2:

Py_buffer buffer;
int res = PyBuffer_FillInfo(&buffer, 0, data, dataSize, true, PyBUF_CONTIG_RO);
if (res == -1) {
    PyErr_Print();
    exit(EXIT_FAILURE);
}
boost::python::object memoryView(boost::python::handle<>(PyMemoryView_FromBuffer(&buffer)))

Python >= 3.3:

The best way I know how is to use PyMemoryView_FromMemory:

boost::python::object memoryView(boost::python::handle<>(PyMemoryView_FromMemory(data, dataSize, PyBUF_READ)));

memoryview is the Python way to access objects that support the buffer interface.

C API memoryview memoryview class

edited Apr 14, 2014 at 19:03

answered Apr 14, 2014 at 17:59

brookskd

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