[New-bugs-announce] [issue42408] passing memoryview slice to struct packing functions

[Daniel Hrisca]

New submission from Daniel Hrisca <daniel.hrisca at gmail.com>:

First I have to apologize if this was discussed before; I've searched the issues and googled the problem but I got nothing obvious.

I'm trying to pass a memoryview slice as argument to struct packing functions to avoid creating intermediate bytes objects

from struct import Struct
s = Struct('<2Q500s').pack_into
buffer = bytearray(7000)
data = bytes(300)
s(buffer, 0, 500, 500, memoryview(data)[4:])


and I get this error:
error: argument for 's' must be a bytes object

Why is it not possible to use memoryviews in this case? 

It is also strange for me that we can use a memoyview as the target buffer, so this works fine:

s(memoryview(buffer)[10:], 0, 500, 500, data[4:])

----------
messages: 381413
nosy: danielhrisca
priority: normal
severity: normal
status: open
title: passing memoryview slice to struct packing functions

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue42408>
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