只需从并集中减去交集即可:
In [1]: a = set([1, 2, 3])
In [2]: b = set([2, 4, 5])
In [3]: c = set([3, 2, 6])
In [4]: (a | b | c) - (a & b & c)
Out[4]: set([1, 3, 4, 5, 6])
或者,推广到任意集合的集合:
In [10]: l = [a, b, c]
In [11]: reduce(set.union, l) - reduce(set.intersection, l)
Out[11]: set([1, 3, 4, 5, 6])
or:
In [13]: set.union(*l) - set.intersection(*l)
Out[13]: set([1, 3, 4, 5, 6])
(后者可能更可取。)