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Date: Mon, 15 Apr 2013 11:29:17 +1000
Subject: Re: howto remove the thousand separator
From: Chris Angelico <rosuav@gmail.com>
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Xref: csiph.com comp.lang.python:43592

On Mon, Apr 15, 2013 at 11:14 AM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> On Sun, 14 Apr 2013 17:44:28 -0700, Mark Janssen wrote:
>> What on earth makes you think that is an O(n**2) algorithm and not O(n)?
>
> Python *might* optimize the first concatenation, '' + 'fe', to just reuse
> 'fe', (but it might not). Let's assume it does, so that no copying is
> needed. Then it gets to the second concatenation, and now it has to copy
> characters, because strings are immutable and cannot be modified in
> place.

There are actually a lot of optimizations done, so it might turn out
to be O(n) in practice. But strictly in the Python code, yes, this is
definitely O(n*n).

ChrisA