I’m pretty sure the ‘power of 2’ advice is based on an error in editing, and should not be taken as a requirement.
That specific piece of advice was added to the Python 2.5 documentation (and backported to Python 2.4.3 docs), in response to Python issue #756104. The reporter was using an unreasonably large buffer size for socket.recv(), which prompted the update.
It was Tim Peters that introduced the ‘power of 2’ concept:
I expect you’re the only person in history to try passing such
a large value to recv() — even if it worked, you’d almost
certainly run out of memory trying to allocate buffer space for
1.9GB. sockets are a low-level facility, and it’s common to
pass a relatively small power of 2 (for best match with
hardware and network realities).
(Bold emphasis mine). I’ve worked with Tim and he has a huge amount of experience with network programming and hardware, so generally speaking I’d take him on his word when making a remark like that. He was particularly ‘fond’ of the Windows 95 stack, he called it his canary in a coalmine for its ability to fail under stress. But note that he says it is common, not that it is required to use a power of 2.
It was that wording that then led to the documentation update:
This is a documentation bug; something the user should be
“warned” about.This caught me once, and two different persons asked about
this in #python, so maybe we should put something like the
following in the recv() docs.“””
For best match with hardware and network realities, the
value of “buffer” should be a relatively small power of 2,
for example, 4096.
“””If you think the wording is right, just assign the bug to
me, I’ll take care of it.
No one challenged the ‘power of 2’ assertion here, but the editor moved from it is common to should be in the space of a few replies.
To me, those proposing the documentation update were more concerned with making sure you use a small buffer, and not whether or not it is a power of 2. That’s not to say it is not good advice however; any low-level buffer that interacts with the kernel benefits with alignment with the kernel data structures.
But although there may well be an esoteric stack where buffers with a size that is a power of 2 matters even more, I doubt Tim Peters ever meant for his experience (that it is common practice) to be cast in such iron-clad terms. Just ignore it if a different buffer size makes more sense for your specific use cases.