[Numpy-discussion] For loop tips

Keith Goodman kwgoodman at gmail.com
Tue Aug 29 14:27:34 CDT 2006

On 8/29/06, Tim Hochberg <tim.hochberg at ieee.org> wrote:
> Keith Goodman wrote:
> > I have a very long list that contains many repeated elements. The
> > elements of the list can be either all numbers, or all strings, or all
> > dates [datetime.date].
> >
> > I want to convert the list into a matrix where each unique element of
> > the list is assigned a consecutive integer starting from zero.
> >
> If what you want is that the first unique element get's zero, the second
> one, I don't think the code below will work in general since the dict
> does not preserve order. You might want to look at the results for the
> character case to see what I mean. If you're looking for something else,
> you'll need to elaborate a bit. Since list2index doesn't return
> anything, it's not entirely clear what the answer consists of. Just idx?
> Idx plus uL?

The output I wanted (in my mind, but unfortunately not in my previous
email) is idx and uL where uL[0] corresponds to the zeros in idx,
uL[1] corresponds to the ones in idx. etc.

I'd also like the uL's to be ordered (now I see that characters and
dates aren't ordered, ooops, thanks for telling me about that). Or
optionally ordered by a second list input which if present would be
used instead of the unique values of L.

Thank you all for the huge improvements to my code. I'll learn a lot
studying all of them.

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