Python 求List的交集，并集，差集.

Python 求List的交集，并集，差集

1.获取两个list 的交集

#方法一:

a=[1，2，6，3，4，5]
b=[2, 5, 12]
temp = [i for i in a if i in b]
print temp
#[2，5]

#方法二

print list(set(a).intersection(set(b))) 

2.获取两个list 的并集

print list(set(a).union(set(b)))

3.获取两个 list 的差集

print list(set(b).difference(set(a)))

扩展阅读：
python的set和其他语言类似, 是一个无序不重复元素集, 基本功能包括关系测试和消 除重复元素. 集合对象还支持union(联合), intersection(交), difference(差)和 sysmmetric difference(对称差集)等数学运算：

Operation	Equivalent	Result
s.update(t)	s |= t	return set s with elements added from t
s.intersection_update(t)	“s &= t”	return set s keeping only elements also found in t
s.difference_update(t)	“s -= t”	return set s after removing elements found in t
s.symmetric_difference_update(t)	“s ^= t	return set s with elements from s or t but not both
s.add(x)		add element x to set s
s.remove(x)		remove x from set s; raises KeyError if not present
s.discard(x)		removes x from set s if present
s.pop()		remove and return an arbitrary element from s; raises KeyError if empty
s.clear()		remove all elements from set s