Commit 69b29d1

Why are Unicode strings better on Python 3?

- it is not the default string type (you have to prefix the string

with a u to get Unicode);

- it is missing some functionality, e.g. casefold;

- there are two distinct implementations, narrow builds and wide builds;

- wide builds take up to four times more memory per string as needed;

- narrow builds take up to two times more memory per string as needed;

- worse, narrow builds have very naive (possibly even "broken")

handling of code points in the Supplementary Multilingual Planes.

The unicode string type in Python 3 is better because:

- it is the default string type;

- it includes more functionality;

- starting in Python 3.3, it gets rid of the distinction between

narrow and wide builds;

- which reduces the memory overhead of strings by up to a factor

of four in many cases;

- and fixes the issue of SMP code points.

(quote from a mailing list post by Steve D'Aprano on 2014-01-17).