[Python-ideas] String and bytes bitwise operations

[Chris Angelico]

On Sat, May 19, 2018 at 2:32 AM, Chris Barker via Python-ideas
<python-ideas at python.org> wrote:
> On Thu, May 17, 2018 at 11:07 PM, Greg Ewing <greg.ewing at canterbury.ac.nz>
> wrote:
>>
>> Steven D'Aprano wrote:
>>>
>>> But XORing bytes seems perfectly reasonable. Bytes are numbers, even if
>>> we display them as ASCII characters.
>
>
> actually, bytes are, well, bytes ;-) -- that is, 8 bits.

Grammatically, you appear to be disagreeing with the assertion that
bytes are numbers. Is that the case?

If you want to be extremely technical, an "octet" is a group of eight
bits (or eight musicians, but I haven't yet figured out how to send
musicians down an ethernet cable), and a "byte" isn't as rigidly
defined. But on modern PCs, you can fairly safely assume that they're
synonymous. I suppose you could argue that a "byte" is a patch of
storage capable of holding a number from 0 to 255, as opposed to being
the number itself, but that's getting rather existential :)

In Python, a "bytes" object represents a sequence of eight-bit units.
When you subscript a bytes [1], you get back an integer with the value
at that position. So if a collection of them is called a "bytes" and
one of them is an integer in range(0, 256), doesn't it stand to reason
that a byte is a number?

Maybe I'm completely misunderstanding your statement here.

ChrisA

[1] Yes, I'm aware that older versions of Python behaved differently. [2]
[2] I'm also aware that putting square brackets after the word "bytes"
could be interpreted as subscripting the 'bytes' type itself, rather
than creating a reference to a footnote. Ain't contextual grammar fun?