[Python-Dev] bytes type discussion (original) (raw)

Guido van Rossum guido at python.org
Wed Feb 15 01:17:11 CET 2006

On 2/14/06, Bob Ippolito <bob at redivi.com> wrote:

On Feb 14, 2006, at 3:13 PM, Guido van Rossum wrote: > - we need a new PEP; PEP 332 won't cut it > > - no b"..." literal > > - bytes objects are mutable > > - bytes objects are composed of ints in range(256) > > - you can pass any iterable of ints to the bytes constructor, as long > as they are in range(256)

Sounds like array.array('B').

Sure.

Will the bytes object support the buffer interface?

Do you want them to?

I suppose they should not support the text part of that API.

Will it accept objects supporting the buffer interface in the constructor (or a class method)? If so, will it be a copy or a view? Current array.array behavior says copy.

bytes() should always copy -- thanks for asking.

> - longs or anything with an index method should do, too > > - when you index a bytes object, you get a plain int

When slicing a bytes object, do you get another bytes object or a list? If its a bytes object, is it a copy or a view? Current array.array behavior says copy.

Another bytes object which is a copy.

(Why would you even think about views here? They are evil.)

> - repr(bytes[1,0 20, 30]) == 'bytes([10, 20, 30])' > > Somewhat controversial: > > - it's probably too big to attempt to rush this into 2.5 > > - bytes("abc") == bytes(map(ord, "abc")) > > - bytes("\x80\xff") == bytes(map(ord, "\x80\xff")) == bytes([128, > 256])

It would be VERY controversial if ord('\xff') == 256 ;)

Oops. :-)

> Very controversial: > > - bytes("abc", "encoding") == bytes("abc") # ignores the "encoding" > argument > > - bytes(u"abc") == bytes("abc") # for ASCII at least > > - bytes(u"\x80\xff") raises UnicodeError > > - bytes(u"\x80\xff", "latin-1") == bytes("\x80\xff") > > Martin von Loewis's alternative for the "very controversial" set is to > disallow an encoding argument and (I believe) also to disallow Unicode > arguments. In 3.0 this would leave us with s.encode() as the > only way to convert a string (which is always unicode) to bytes. The > problem with this is that there's no code that works in both 2.x and > 3.0.

Given a base64 or hex string, how do you get a bytes object out of it? Currently str.decode('base64') and str.decode('hex') are good solutions to this... but you get a str object back.

I don't know -- you can propose an API you like here. base64 is as likely to encode text as binary data, so I don't think it's wrong for those things to return strings.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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