[Duane] > LoTuples1 = [(1,1,0),(1,2,1),(1,3,3)] > Set1=set(LoTuples1) > LoTuples2 = [(2,1,3),(2,2,4),(2,3,2)] > Set2=set(LoTuples2) > > What I would like to be able to do is: > > Set3 = Set1union(Set2) > Set3.intersection(Set2, <use object[2]>) > > to return: > set([(2,1,3), (1,3,3)]) > > How can one do this operation?
Conceptually, there is more than one operation going on. First, finding the attributes shared in both sets: ca = set(t[2] for t in LoTuples1) & set(t[2] for t in LoTuples2) which gives: set([3]) Second, find any tuple which has that attribute (including multiple results for the same attribute): set(t for t in (LoTuples1 + LoTuples2) if t[2] in ca) which returns: set([(2, 1, 3), (1, 3, 3)]) Wanting multiple results for the same attribute value (i.e. both (2,1,3) and (1,3,3) have 3 in the second position) is why multiple steps are needed; otherwise, the behavior of intersection() is to return a single representative of the equivalence class. Raymond -- http://mail.python.org/mailman/listinfo/python-list
