[Python-Dev] bitwise operations for bytes and bytearray (original) (raw)

Cameron Simpson cs at zip.com.au
Thu Jan 7 20:08:20 EST 2016

On 07Jan2016 16:12, Python-Dev <python-dev at python.org> wrote:

On Jan 7, 2016, at 15:57, Martin Panter <vadmium+py at gmail.com> wrote:

On 7 January 2016 at 22:26, Blake Griffith <blake.a.griffith at gmail.com> wrote: I'm interested in adding the functionality to do something like:

b'a' ^ b'b' b'\x03' Instead of the good ol' TypeError. I think both bytes and bytearray should support all the bitwise operations. There is a bug open about adding this kind of functionality: <https://bugs.python.org/issue19251>. And it's in the needs patch stage, which makes it perfect for the OP: in addition to learning how to hack on builtin types, he can also learn the other parts of the dev process. (Even if the bug is eventually rejected, as seems likely given that it sat around for three years with no compelling use case and then Guido added a "very skeptical" comment.)

The use case which springs immediately to my mind is cryptography. To encrypt a stream symmetrically you can go:

cleartext-bytes ^ cryptographicly-random-bytes-from-cipher

so with this one could write:

def crypted(byteses, crypto_source): ''' Accept an iterable source of bytes objects and a preprimed source of crypto bytes, yield encrypted versions of the bytes objects. ''' for bs in byteses: cbs = crypto_source.next_bytes(len(bs)) yield bs ^ cbs

Cheers, Cameron Simpson <cs at zip.com.au>

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