两个列表取差集

Question

list1 = ['1', '2', '3', '4']
list2 = ['1', '2', '5', '6']

求取差集：

['3', '4', '5', '6']

Answer 1

list(set(list1)^set(list2))

Answer 2

list( set(list1).symmetric_difference(list2) )

Answer 3

list1 = ['1', '2','3','4']
list2 = ['1', '2', '5', '6']
set1 = set(list2) - set(list1)
set2 = set(list1) - set(list2)
newlist =  list(set1)+list(set2)
print sorted(newlist)

应该还有更简洁的方法.