[Python-Dev] defaultdict proposal round three (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Tue Feb 21 10:59:06 CET 2006

Bengt Richter wrote:

you could write

d = dict()**list

Or alternatively,

ld = dict[list]

i.e. "a dict of lists". In the maximally twisted form of this idea, the result wouldn't be a dict but a new type of dict, which you would then instantiate:

d = ld(your_favourite_args_here)

This solves both the constructor-argument problem (the new type can have the same constructor signature as a regular dict with no conflict) and the perceived-Liskov-nonsubstitutability problem (there's no requirement that the new type have any particular conceptual and/or actual inheritance relationship to any other type). Plus being a really cool introduction to the concepts of metaclasses, higher-order functions and all that neat head-exploding stuff. :-)

Resolving-not-to-coin-any-more-multihyphenated- hyperpolysyllabic-words-like-'perceived-Liskov- nonsubstitutability'-this-week-ly,

Greg

More information about the Python-Dev mailing list