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Re: how to get bytes from bytearray without copying

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  Re: how to get bytes from bytearray without copying Cameron Simpson <cs@zip.com.au> - 2014-03-04 09:02 +1100

#67592 — Re: how to get bytes from bytearray without copying

On 03Mar2014 09:15, Juraj Ivančić <juraj.ivancic@gmail.com> wrote:
> On 3.3.2014. 1:44, Cameron Simpson wrote:
> >>ValueError: cannot hash writable memoryview object
> >
> >Have you considered subclassing memoryview and giving the subclass
> >a __hash__ method?
> 
> I have, and then, when I failed to subclass it, I considered doing
> aggregation, and make it behave byte-like. But how to implement the
> overridden __hash__ method? It will still require at least *some*
> redundant copying. And there is the slicing thing... the whole idea
> started to feel like I was performing tonsillectomy through the anal
> cavity.

Write a wrapper class instead and use:

  def __hash__(self):
    return id(self)

Simple and fast. Unless you need slices with the same content to
hash the same (eg storing them as dict keys, or in sets).

And alternative would be a simple hash of the first few bytes in
whatever slice you had.

Cheers,
-- 
Cameron Simpson <cs@zip.com.au>

Why is it so hard for people to simply leave people alone? But, the answer
comes to me: they are idiots and in a perfect world, I would be permitted to
kill them all.  - Julie Rhodes <jk.rhodes@asacomp.com>

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