[Python-ideas] keyfuncdict -- the good, the bad, and the ugly

[Raymond Hettinger]

Was thinking of all the things that could be done with Antoine's generalization:

The Good
========
d = keyfuncdict(key=str.lower)        # case insensitive dict

def track(obj):
    logging.info(obj)
    return obj
d = keyfuncdict(key=track)               # monitored dict

d = keyfuncdict(key=id)                          # makes benjamin happy


The Bad
=======

d = keyfuncdict(key=tuple)                    # lets you use lists as keys

d = keyfuncdict(key=repr)                     # support many kinds of mutable or unhashable keys

d = keyfuncdict(key=pickle.loads)       # use anything picklable as a key

d = keyfuncdict(key=getuser)               # track one most recent entry per user


The Ugly
========

d = keyfuncdict(key=random.random)           # just plain weird

d = keyfuncdict(key=itertools.count().next)   # all entries are unique and unretrievable ;-)

def remove(obj):
     d.pop(obj)
     return obj
d = keyfuncdict(key=remove)                          # self deleting dict ;-)


Raymond