Message 170818 - Python tracker (original) (raw)

There's probably a bigger discussion about memoryviews for a rainy day. However, the number one thing that would save all of this in my book would be to make sure cast('B') is universally supported regardless of format including endianness--especially in the standard library. For example, being able to do this:

a = array.array('d',[1.0, 2.0, 3.0, 4.0]) m = memoryview(a).cast('B') m[0:4] = b'\x00\x01\x02\x03' a array('d', [1.0000000112050316, 2.0, 3.0, 4.0])

Right now, it doesn't work for ctypes. For example:

import ctypes a = (ctypes.c_double * 4)(1,2,3,4) a <__main__.c_double_Array_4 object at 0x1006a7cb0> m = memoryview(a).cast('B') Traceback (most recent call last): File "", line 1, in ValueError: memoryview: source format must be a native single character format prefixed with an optional '@'

As some background, being able to work with a "byte" view of memory is important for a lot of problems involving I/O, data interchange, and related problems where being able to accurately construct/deconstruct the underlying memory buffers is more useful than actually interpreting their contents.