list index()

Chris Mellon arkanes at gmail.com
Fri Aug 31 01:48:28 CEST 2007


On 8/30/07, zzbbaadd at aol.com <zzbbaadd at aol.com> wrote:
> On Aug 30, 4:31 pm, Ben Finney <bignose+hates-s... at benfinney.id.au>
> wrote:
> > zzbba... at aol.com writes:
> > > In my case of have done os.listdir() on two directories. I want to see
> > > what files are in directory A that are not in directory B.
> >
> > You get that information unambiguously. It's an exceptional case,
> > since there's no index to return, so it throws an exception.
> >
> > > I have used exceptions in other languages and only do so on logic
> > > that should never happen.
> >
> > You're confusing "assert" ("this should always be true") with
> > "exception" ("this is an exception to the the normal flow of this
> > process").
> >
> > An exception isn't "something that should never happen", it's
> > something that is entirely possible and needs to be handled somehow.
>
> I don't think that is the definition used across computer science.
>

how its defined in Python is what is important in this context.

> It suddenly dawned on me that what would be best would be a contains()
> (or IN syntax for those who can't afford to wait) for lists.
>
> if mylist.contains("hello):
>

Genius. Why didn't anyone think of that before?



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