[Python-ideas] grouping / dict of lists

[Serhiy Storchaka]

30.06.18 00:42, Guido van Rossum пише:
> On a quick skim I see nothing particularly objectionable or 
> controversial in your PEP, except I'm unclear why it needs to be a class 
> method on `dict`. Adding something to a builtin like this is rather 
> heavy-handed. Is there a really good reason why it can't be a function 
> in `itertools`? (I don't think that it's relevant that it doesn't return 
> an iterator -- it takes in an iterator.)
> 
> Also, your pure-Python implementation appears to be O(N log N) if key is 
> None but O(N) otherwise; and the version for key is None uses an extra 
> temporary array of size N. Is that intentional?

And it adds a requirement to keys be orderable.

I think there should be two functions with different requirements: for 
hashable and orderable keys. The latter should return a list of pairs or 
a sorted dict if they be supported by the stdlib.

I'm not sure they fit well for the itertools module. Maybe the purposed 
algorithms module would be a better place. Or maybe just keep them as 
recipes in the documentation (they are just few lines). Concrete 
implementation can be simpler than the general implementation.