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Date: Sun, 19 Aug 2012 18:24:57 +1000
Subject: Re: How do I display unicode value stored in a string variable using ord()
From: Chris Angelico <rosuav@gmail.com>
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Xref: csiph.com comp.lang.python:27362

On Sun, Aug 19, 2012 at 6:11 PM, Paul Rubin <no.email@nospam.invalid> wrote:
> Steven D'Aprano <steve+comp.lang.python@pearwood.info> writes:
>>     result = text[end:]
>
> if end not near the end of the original string, then this is O(N)
> even with fixed-width representation, because of the char copying.
>
> if it is near the end, by knowing where the string data area
> ends, I think it should be possible to scan backwards from
> the end, recognizing what bytes can be the beginning of code points and
> counting off the appropriate number.  This is O(1) if "near the end"
> means "within a constant".

Only if you know exactly where the end is (which requires storing and
maintaining a character length - this may already be happening, I
don't know). But that approach means you need to have code for both
ways (forward search or reverse), and of course it relies on your
encoding being reverse-scannable in this way (as UTF-8 is, but not
all).

And of course, taking the *entire* rest of the string isn't the only
thing you do. What if you want to take the next six characters after
that index? That would be constant time with a fixed-width storage
format.

ChrisA