reversing a dictionary (newbie)

[piet at cs.uu.nl]

>>>>> "Christopher Brewster" <C.Brewster at dcs.shef.ac.uk> (CB) writes:

CB> def revdict(diction):
CB> 	revdict = {}
CB> 	for wordpair in diction.keys():
CB> 		#print wordpair
CB> 		list = []
Why start with an empty list? See below
CB> 		freq = diction[wordpair]
CB> 		if revdict.has_key(freq):
CB> 			list.extend(revdict[freq])
                        The list was empty, so list=revdict[freq] would be faster
CB> 			list.append(wordpair)
CB> 			revdict[freq] = list
                        But of course revdict[freq].append(wordpair) would
                        be even better instead of the 3 lines above.
CB> 		else:
CB> 			list.append(wordpair)
                        Here the same. list=[wordpair] would be the same
CB> 			revdict[freq] = list
                        But then revdict[freq]=[wordpair] would be the fastest.
CB> 	return revdict

-- 
Piet van Oostrum <piet at cs.uu.nl>
URL: http://www.cs.uu.nl/~piet [PGP]
Private email: P.van.Oostrum at hccnet.nl