pep3118 | 易学教程

Why is it not possible to get a Py_buffer from an array object?

阅读更多关于 Why is it not possible to get a Py_buffer from an array object?

问题 The python documentation on array clearly states that the array conforms to the buffer interface. It even suggest not using the buffer_info() method. But when I try to get a Py_Buffer from C/C++ code with PyObject_GetBuffer() or use python's memoryview, I get a failure. For example, in python (I use version 2.7): >>> a = array.array('c') >>> memoryview(a) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: cannot make memory view because object does not have the

Why is it not possible to get a Py_buffer from an array object?

阅读更多关于 Why is it not possible to get a Py_buffer from an array object?

Assignment into Python 3.x Buffers with itemsize > 1

阅读更多关于 Assignment into Python 3.x Buffers with itemsize > 1

问题 I am trying to expose a buffer of image pixel information (32 bit RGBA) through the Python 3.x buffer interface. After quite a bit of playing around, I was able to get this working like so: int Image_get_buffer(PyObject* self, Py_buffer* view, int flags) { int img_len; void* img_bytes; // Do my image fetch magic get_image_pixel_data(self, &img_bytes, &img_len); // Let python fill my buffer PyBuffer_FillInfo(view, self, img_bytes, img_len, 0, flags); } And in python I can play with it like so:

Cython - Memoryview of a dynamic 2D C++Array

阅读更多关于 Cython - Memoryview of a dynamic 2D C++Array

问题 The Goal: Get a Memoryview from a 2D C++ char array using Cython. A little background: I have a native C++ library which generates some data and returns it via a char** to the Cython world. The array is initialized and operated in the library about like this: struct Result_buffer{ char** data_pointer; int length = 0; Result_buffer( int row_capacity) { data_pointer; = new char*[row_capacity]; return arr; } // the actual data is appended row by row void append_row(char* row_data) { data_pointer

Using Py_buffer and PyMemoryView_FromBuffer with different itemsizes

阅读更多关于 Using Py_buffer and PyMemoryView_FromBuffer with different itemsizes

问题 This question is related to a previous question I asked. Namely this one if anyone is interested. Basically, what I want to do is to expose a C array to Python using a Py_buffer wrapped in a memoryview -object. I've gotten it to work using PyBuffer_FillInfo (work = I can manipulate the data in Python and write it to stdout in C), but if I try to roll my own buffer I get a segfault after the C function returns. I need to create my own buffer because PyBuffer_FillInfo assumes that the format is

PEP 3118 warning when using ctypes array as numpy array

阅读更多关于 PEP 3118 warning when using ctypes array as numpy array

问题 I'm getting the following warning message when I try to use a ctypes array as a numpy array: Python 2.7.1 (r271:86832, Nov 27 2010, 18:30:46) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> import ctypes, numpy >>> TenByteBuffer = ctypes.c_ubyte * 10 >>> a = TenByteBuffer() >>> b = numpy.ctypeslib.as_array(a) C:\Python27\lib\site-packages\numpy\ctypeslib.py:402: RuntimeWarning: Item size computed from the PEP 3118 buffer format

PEP 3118 warning when using ctypes array as numpy array

阅读更多关于 PEP 3118 warning when using ctypes array as numpy array

I'm getting the following warning message when I try to use a ctypes array as a numpy array: Python 2.7.1 (r271:86832, Nov 27 2010, 18:30:46) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> import ctypes, numpy >>> TenByteBuffer = ctypes.c_ubyte * 10 >>> a = TenByteBuffer() >>> b = numpy.ctypeslib.as_array(a) C:\Python27\lib\site-packages\numpy\ctypeslib.py:402: RuntimeWarning: Item size computed from the PEP 3118 buffer format string does not match the actual item s ize. return array(obj, copy=False) >>> b array([0, 0, 0, 0, 0, 0