[issue19251] bitwise ops for bytes of equal length

[Cameron Simpson]

Cameron Simpson added the comment:

I'd like speak my support for bitwise ops on bytes and bytearray (agree, on equal lengths only).

I've got 2 arguments here:

- readability: a ^ b, a | b and so forth are clear and direct

- all the various incantation presented must be _understood_, not to mention invented anew by anyone wanting to do they same, with the same burden of getting it correct; of course one can say the same of any feature not already present in a language but that is trite; there are several ways to say this and all have varying degrees of speed, obtuseness and verbosity. And they're all SLOW.

Regarding some of the counter arguments in the discussion:

- gregory.p.smith in reply to cowlicks: "Security claims?  Nonsense. This has nothing to do with security.  It is *fundamentally impossible* to write constant time side channel attack resistant algorithms [...]"

Maybe cowlicks should have said "reliable", though to my naive eye a normal implementation would be constant time for a given size. I would argue that the clarity and directness of just writing "a^b" immediately makes for trivially correct code, which itself is a necessary prerequisite for secure code.

- gregory.p.smith again: "Neither of the above "look as nice" as a simple operator would. But they are at least both understandable and frankly about the same as what you would naively write in C for the task."

This is not an argument against the feature. That one had to perform similar activitie in Python as in C merely reflects the present lack of these operators, not a preexisting gleaming sufficiency of operator richness.

- Terry J. Reddy: "'XOR of two bytes in one place' strikes me as a thin excuse for a new feature that abbreviates a simple, short, one-liner". Christian Heimes's code has this single example, but anyone wanting to work on chunks of bytes may find themselves here. Just because a lot of things can be written/constructed as one liners doesn't mean they should be operators when (a) the operator is available (==unused) for this type, (b) the meaning of the operator is straight forward and intuitive and (c) any pure Python construction is both wordier and much slower.

Anyway, I an for this feature, for the record.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue19251>
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