[Python-Dev] Byte literals (was Re: [Python-checkins] Changing string constants to byte arrays ( r55119 (original) (raw)

[Python-Dev] Byte literals (was Re: [Python-checkins] Changing string constants to byte arrays ( r55119 - in python/branches/py3k-struni/Lib: codecs.py test/test_codecs.py ))

Fred L. Drake, Jr. fdrake at acm.org
Sat May 5 19:34:44 CEST 2007

On Saturday 05 May 2007, Aahz wrote:

I'm with MAL and Fred on making literals immutable -- that's safe and lots of newbies will need to use byte literals early in their Python experience if they pick up Python to operate on network data.

Yes; there are lots of places where bytes literals will be used the way str literals are today. buffer(b'...') might be good enough, but it seems more than a little idiomatic, and doesn't seem particularly readable.

I'm not suggesting that /all/ literals result in constants, but bytes literals seem like a case where what's wanted is the value. If b'...' results in a new object on every reference, that's a lot of overhead for a network protocol implementation, where the data is just going to be written to a socket or concatenated with other data. An immutable bytes type would be very useful as a dictionary key as well, and more space-efficient than tuple(b'...').

Whether there should be one type with a flag indicating mutability, or two separate types (as with set and frozenset), I'm not sure. The later offers some small performance benefits, but I don't expect there's enough to really matter there.

-Fred

-- Fred L. Drake, Jr.

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