[Python-3000] Immutable bytes -- looking for volunteer (original) (raw)

Guido van Rossum guido at python.org
Tue Sep 25 23:32:05 CEST 2007

On 9/25/07, Guido van Rossum <guido at python.org> wrote:

OK, Jeffrey's and Adam's patches were helpful; it looks like the damage done by making bytes immutable is pretty limited: plenty of modules are affected, but the changes are straightforward and localized.

So now I have an idea that goes a little farther. It relates to Talin's response (second message in this thread if you're using gmail) and acknowledges that there are some good use cases for mutable bytes as well (as I've always maintained). How about we take the existing PyString implementation (Python 2's str, currently still present as str8 in py3k), remove the locale and unicode mixing support, and call it bytes. Then the PyBytes type can be renamed to buffer. It is well-documented that I don't care much about the existing buffer() builtin; it can be renamed to memview for all I care (that would be a more descriptive name anyway).

D'oh. Travis already implemented a memoryview object that has most of the required properties. So let's use that instead of memview or the old buffer object.

This would provide a much better transitional path for 2.x code manipulating raw bytes using str instances: just change "..." into b"..." and str into bytes. (Of course, 2.x code that is confused about bytes vs. characters will fail hard in 3.0 as soon as a bytes and a str instance meet -- this is already the case in the current 3.0 code base and will remain unchanged.)

It would mean more fixes beyond what Jeffrey and Adam did, since iterating over a bytes instance would return a bytes instance of length 1 instead of a small int, and the bytes constructor would change accordingly (no more initializing a bytes object from a list of ints). The (new) buffer object would also have to change to be more compatible with the (new) bytes object -- bytes<-->buffer conversions should be 1-1, and iterating over a buffer instance would also have to return a length-1 buffer (or bytes???) instance. Thoughts?

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

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