Pre-PEP: Dictionary accumulator methods

[Michael Spencer]

Raymond Hettinger wrote:
> I would like to get everyone's thoughts on two new dictionary methods:

+1 count
? appendlist

> 
> The proposed names could possibly be improved (perhaps tally() is more active
> and clear than count()).

IMO 'tally' is exactly the right method name

One issue is with negative increments reaching zero i.e., deleting the key once 
the tally goes to 0: this behavior would match the automatic key creation.

> The appendlist() method is not as versatile as setdefault() which can be used

Simpler list initialization augmentation would be very handy - but I would also 
like the equivalent functionality sets (don't care about dicts of dicts though).

Given the difference in set/list augmentation methods, this may present a 
challenge.  Alternatively, perhaps dict_of_list and dict_of_set could become 
specialized containers - they might then have value_append/value_extend and 
value_add methods respectively.  I imagine (without any basis in fact) that it 
would also be possible the optimize the performance of large mappings of 
containers compared with the generic dict.


Michael