[Python-ideas] Fwd: grouping / dict of lists
chris.barker at noaa.gov
Mon Jul 9 12:22:03 EDT 2018
On Fri, Jul 6, 2018 at 12:26 PM, Franklin? Lee I use this kind of function
in several different projects over the
> years, and I rewrote it many times as needed.
> I added several options, such as:
> - key function
> - value function
> - "ignore": Skip values with these keys.
> - "postprocess": Apply a function to each group after completion.
> - Pass in the container to store in. For example, create an
> OrderedDict and pass it in. It may already hold items.
> - Specify the container for each group.
> - Specify how to add to the container for each group.
> Then I cut it down to two optional parameters:
> - key function. If not provided, the iterable is considered to have
> key-value pairs.
OK -- seems we're all converging on that :-)
> - The storage container.
so this means you'r passing in a full set of storage containers? I'm a vit
confused by that -- if they might be pre-populated, then they would need to
be instance,s an you'd need to have one for every key -- how would you know
in advance aht you needed???
I played around with passing in a optional storage object:
but as we might want a list or a set, or a Counter, or ??? it got pretty
ugly, as lists and sets and Counters all have different APIs for adding
stuff. So I gave up and figured just saying "it's always a list) made the
> Finally, I removed the key function, and only took pairs and an
> optional container. However, I don't remember why I removed the key
> function. It may be that I was writing throwaway lambdas, and I
> decided I might as well just write the transformation into the
exactly -- but I suspect hat may be because you where writing a
comprehension anyway, as you needed to manipulate the values, also -- so if
there were a value function, you could use either API.
> I think a key function is worth having.
I think there's more or less consensus on that too.
Christopher Barker, Ph.D.
Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception
Chris.Barker at noaa.gov
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Python-ideas