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Date: Mon, 28 Oct 2013 22:18:45 +1100
Subject: Re: how to avoid checking the same condition repeatedly ?
From: Chris Angelico <rosuav@gmail.com>
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Xref: csiph.com comp.lang.python:57811

On Mon, Oct 28, 2013 at 10:14 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> if needs_preprocessing:
>     for elem in iterable:
>         # If you change this block, you must remember to change the
>         # block below too!
>         preprocess(item)
>         do_this(item)
>         do_that(item)
>         do_something_else(item, arg1, arg2, expression)
>         do_another_thing(item + arg3, key=whatever)
>         print(item)
> else:
>     for elem in iterable:
>         # If you change this block, you must remember to change the
>         # block above too!
>         preprocess(item)
>         do_this(item)
>         do_that(item)
>         do_something_else(item, arg1, arg2, expression)
>         do_another_thing(item, key=whatever)
>         print(item)
>
>
> The careful reader will notice that there's already a bug in this.

For a start, you're preprocessing in the second block... I don't think
that was your intentional bug :)

ChrisA