I tried this code:
old_dict = {'xyz':['a','b','c'],'baz':['c','d']}
new_dict = {}
for dkey, vallist in old_dict.iteritems():
for val in vallist:
if val in new_dict:
theset = new_dict[val]
theset.add(dkey)
new_dict[val] = theset
else:
new_dict[val] = set([dkey])
print new_dict
Which yields the output {'a': set(['xyz']), 'c': set(['xyz', 'baz']),
'b': set(['xyz']), 'd': set(['baz'])}, so it seems to work but I have a
feeling this is a crappy solution that's underusing Python. Please
enlighten me of a better way!
In python2.5, collections.defaultdict was added which could clean
this up a bit:
import collections
# using a set to remove duplication
new_dict = collections.defaultdict(set)
for dkey, vallist in old_dict.iteritems():
for val in vallist:
new_dict[val].add(dkey)
# using a list to keep all keys
new_dict = collections.defaultdict(list)
for dkey, vallist in old_dict.iteritems():
for val in vallist:
new_dict[val].append(dkey)
If you're working in pre-2.5 python, you could use
new_dict = {}
...
# use a set()
new_dict.setdefault(val, set()).add(dkey)
# use a list()
new_dict.setdefault(val, []).append(dkey)
-tkc
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