In my mind, I *rarely* (which is more than never) have my data in the form of a sequence of key/value pairs. The version of the API that assumes data starts that way feels like either a niche case, or demands preprocessing before it's ready to pass to grouping() or collections.Grouping().
That said, an identity key is rarely interesting either. So I think have key=None mean "assume we get key/val pairs is harmless to the more common case where we give an explicit key function. The uncommon need for grouping on equality can be handled with 'key=lambda x: x'. On Mon, Jul 9, 2018, 12:22 PM Chris Barker <chris.bar...@noaa.gov> wrote: > 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. >> > > interesting... > > >> 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: > > > https://github.com/PythonCHB/grouper/commit/d986816905406ec402724beaed2b88c96df64469 > > 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 > most sense. > > >> 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 >> comprehension. > > > 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. > > -CHB > > > > -- > > Christopher Barker, Ph.D. > Oceanographer > > 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.bar...@noaa.gov >
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