How is unicode implemented behind the scenes?

[MRAB]

On 2014-03-09 02:08, Dan Stromberg wrote:
> OK, I know that Unicode data is stored in an encoding on disk.
>
> But how is it stored in RAM?
>
> I realize I shouldn't write code that depends on any relevant
> implementation details, but knowing some of the more common
> implementation options would probably help build an intuition for
> what's going on internally.
>
> I've heard that characters are no longer all c bytes wide internally,
> so is it sometimes utf-8?
>
No.

 From Python 3.3, it's an array of 1, 2 or 4 bytes per codepoint.

In Python terms:

if all(c <= '\xFF' for c in string):
     use 1 byte per codepoint
elif all(c <= '\xFFFF' for c in string):
     use 2 bytes per codepoint
else:
     use 4 bytes per codepoint