Style question (Poll)

Chris Angelico rosuav at gmail.com
Thu Mar 15 01:17:49 CET 2012


On Thu, Mar 15, 2012 at 7:37 AM, Croepha <croepha at gmail.com> wrote:
> Which is preferred:
>
> for value in list:
>  if not value is another_value:
>    value.do_something()
>    break
>
> --or--
>
> if list and not list[0] is another_value:
>  list[0].do_something()
>
> Comments are welcome, Thanks

General principle: Make the code look like what it's doing. I don't
mean text art and making code in the shape of pi that prints the
digits of pi (although that can be awesome too), but more that a loop
should not be used when you don't intend for it to loop. Consider the
For-Case Paradigm[1] and the amazing confusion value that it can
offer. A loop needn't execute more than once (it needn't even execute
the first time), but it should at least have the _potential_ to
execute the same code multiple times, otherwise it's hardly a loop.

I had a particularly nasty example of a loop-that-wasn't-a-loop at
work a while ago; it was PHP, not Python, so I won't share it here,
but it had a do-while loop and an insidious bug in it. Very tricky.

ChrisA
[1] http://thedailywtf.com/Articles/The_FOR-CASE_paradigm.aspx



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