[Python-ideas] Run length encoding

[Neal Fultz]

Agreed to a degree about providing it as code, but it may also be worth
mentioning also that zlib itself implements rle [1], and if there was ever
a desire to  go "python all the way down" you need an RLE somewhere anyway
:)

That said, I'll be pretty happy with anything that replaces an hour of
google/coding/testing/(hour later find out I'm an idiot from a random
listserv) with 1 minute of googling.  Again, my issue isn't that it was
difficult to code, but it *was* hard to make the research-y jump from
googling for "run length encoding python", where I knew *exactly* what
algorithm I wanted, to  "itertools.groupby" which appears to be more
general purpose and needs a little tweaking.  Adjusting the docs/recipes
would probably solve that problem.

 -- To me this is roughly on the same level as googling for 'binary search
python' and not having bisect show up.

However, the fact that  `itertools.groupby` doesn't group over elements
that are not contiguous is a bit surprising to me coming from SQL/pandas/R
land (that is probably a large part of my disconnect here). This is
actually explicitly called out in the current docs, but I wonder how many
people search for one thing and find the other:

 I googled for RLE and the solution was actually groupby, but probably a
lot of other people want a SQL group-by accidentally got an RLE and have to
work around that... Then again, I don't know if you all can easily change
names of functions at this point.

-Neal

[1] https://github.com/madler/zlib/blob/master/deflate.c#L2057



On Sat, Jun 10, 2017 at 9:39 PM, Greg Ewing <greg.ewing at canterbury.ac.nz>
wrote:

> In my experience, RLE isn't something you often find on its own.
> Usually it's used as part of some compression scheme that also
> has ways of encoding verbatim runs of data and maybe other
> things.
>
> So I'm skeptical that it can be usefully provided as a library
> function. It seems more like a design pattern than something
> you can capture in a library.
>
> --
> Greg
>
>
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