[Python-3000] PEP 3137: Immutable Bytes and Mutable Buffer

[Joel Bender]

> **Open Issue:** I'm undecided on whether indexing bytes and buffer
> objects should return small ints (like the bytes type in 3.0a1, and
> like lists or array.array('B')), or bytes/buffer objects of length 1
> (like the str type).  The latter (str-like) approach will ease porting
> code from Python 2.x; but it makes it harder to extract values from a
> bytes array.

The protocol encoding and decoding world calls these "octet strings" and 
it makes encoding and decoding discussions a lot easier.  ASN.1 calls 
them that and it's a good thing.

In that frame of mind, the first element is an octet, and while Python 
would not add a new datatype, just like it doesn't have one for 
character, it would be an unsigned integer in range(256).

> Methods
> -------
> 
> The following methods are supported by bytes as well as buffer, with
> similar semantics.  They accept anything that implements the PEP 3118
> buffer API for bytes arguments, and return the same type as the object
> whose method is called ("self"):

First, please enforce that where these functions take a "string" 
parameter that they require an octet or octet string (I couldn't find 
what kinds of arguments these functions require in PEP 3118):

     >>> x = b'123*45'
     >>> x.find("*")
     TypeError: expected an octet string or int

     >>> x.find(b'*')
     3
     >>> x.find(42)
     3

Second, Please add slice operations and .append() to mutable octet strings:

     >>> x[:0] = b'>'              # start of message
     >>> x.append(sum(x) % 256)    # simple checksum


Joel