[Python-Dev] Re: Candidate Itertools

[David Eppstein]

In article <20040622035255.GB1891 at panix.com>,
 Aahz <aahz at pythoncraft.com> wrote:

> > Hmm, there seems to be 100% support for returning a dictionary and zero
> > support for my iterable (cnt, elem) ... to feed min(), max(), sorted(),
> > nlargest(), and nsmallest().
> 
> The problem is that it's useful for those operations -- and nothing
> else.  It's narrow functionality, and anyone looking just at itertools
> will find this confusing; it's just not the natural definition for
> something named ``count_elements``, and I suspect it is not possible to
> create a good name for your purpose.  Anyone who understands Python will
> expect ``count_elements`` to return (elem,cnt) or a dict.

I finally found the recent code where I'd used something like this
(for the curious: http://www.ics.uci.edu/~eppstein/numth/egypt/egypt.py)

I wrote it as a function that returns a dict (itemCounts in the above 
source) but what I actually did with the results in one place was to 
sort the (elem,cnt) pairs by elem (not by cnt) and then iterate through 
them in sorted order. In another place I used the dictionary directly 
but it amounted to the same thing.

So, either of Aahz's suggestions would have worked for me but the 
original (cnt,elem) suggestion wouldn't have been right.

-- 
David Eppstein                      http://www.ics.uci.edu/~eppstein/
Univ. of California, Irvine, School of Information & Computer Science