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I expect struct.pack_into to work for a memoryview. Currently struct.pack_into throws an exception.
>>> import struct
>>> buf = bytearray(10)
>>> struct.pack_into("<B", buf, 0, 99)
>>> buf[0]
99
>>> view = memoryview(buf)
>>> view.readonly
False
>>> struct.pack_into("<B", view, 0, 88)
Traceback (most recent call last):
 File "<input>", line 1, in <module>
TypeError: expected a writeable buffer object
>>> view[0:1] = 'a'
>>> view[0]
'a'
>>> buf[0]
97
>>> chr(buf[0])
'a'
The memoryview is writeable and from what I can tell from the documentation it implements the buffer interface, but struct.pack_into will not use it.

This works in Python 3.3+. It is a bug in 2.7, so we have to wait for
someone motivated enough to work on an outdated Python version.

This issue is similar to issue10212. Here is a patch which makes struct.pack_into() support new buffer protocol.
Something similar should be applied to 3.x because PyObject_AsWriteBuffer() is deprecated and not safe.

I think you forgot to upload your patch.

Oh, sorry. Here is it.

lgtm :)

Benjamin, what are your thoughts as RM?
> Something similar should be applied to 3.x because PyObject_AsWriteBuffer() is deprecated and not safe.
Done in issue22896.

I suppose this is okay.

New changeset 4d8e37e54a7d by Serhiy Storchaka in branch '2.7':
Issue #22113: struct.pack_into() now supports new buffer protocol (in
https://hg.python.org/cpython/rev/4d8e37e54a7d