[Python-ideas] More useful slices (original) (raw)

Chris Barker chris.barker at noaa.gov
Mon Feb 2 17:35:11 CET 2015

On Mon, Feb 2, 2015 at 8:11 AM, Chris Barker - NOAA Federal < chris.barker at noaa.gov> wrote:

It would be nice if there was more Kongo as to why it was rejected,

Wow -- weird auto-correct! That was supposed to be "info".

That's what I get for trying to write these notes on a phone on the bus...

Sorry,

-Chris

but it was, indeed, rejected.

I also recall a lot of drawn out threads about more compact syntax for a for loop over integers, such as making the integer object iterable: for I in 10: pass Which were also all rejected. Unless someone comes up with a compelling argument that something has changed, it seems this conversation has been had already. -Chris

On Feb 2, 2015, at 7:02 AM, Neil Girdhar <mistersheik at gmail.com> wrote: But it is meaningful to have a range with an unspecified stop. That's itertools.count. On Sunday, February 1, 2015 at 12:27:53 PM UTC-5, Steven D'Aprano wrote: On Sun, Feb 01, 2015 at 04:13:32PM +0100, Todd wrote: > Although slices and ranges are used for different things and implemented > differently, conceptually they are similar: they define an integer sequence > with a start, stop, and step size. I'm afraid that you are mistaken. Slices do not necessarily define integer sequences. They are completely arbitrary, and it is up to the object being sliced to interpret what is or isn't valid and what the slice means. py> class K(object): ... def getitem(self, i): ... print(i) ... py> K()["abc":(2,3,4):{}] slice('abc', (2, 3, 4), {})

In addition, the "stop" argument to a slice may be unspecified until it it applied to a specific sequence, while range always requires stop to be defined. py> s = slice(1, None, 2) py> "abcde"[s] 'bd' py> "abcdefghi"[s] 'bdfh' It isn't meaningful to define a range with an unspecified stop, but it is meaningful to do so for slices. In other words, the similarity between slices and ranges is not as close as you think. -- Steven

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Christopher Barker, Ph.D. Oceanographer

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