I searched for an hour and don't see a solution to this (i assume somewhat common) problem.
I have a very large dictionary of lists: d = {a:[1,2], b:[2,3], c:[3]} and i want to reverse the associativity of the integers thusly: inverse(d) makes {1:[a], 2:[a,b], 3:[b,c]} my solution expands the original dict into two lists of keys and list elements: list1: [a,a,b,b,c] list2: [1,2,2,3,3] then recombines them with the reverse operation. but this takes too much time and a lot of memory. I wonder if anyone can point me to a more efficient solution? -- http://mail.python.org/mailman/listinfo/python-list