list, set操作
def union_list(l1, l2): result = [] if not l1: result.extend(l2) return result if not l2: result.extend(l1) return result result.extend(l1) for i in set(l1+l2): if i not in l1: result.append(i) return result
set(l1+l2) 也可以达到以上目的,但是会重新排序。上述程序保留l1的顺序。
set 的操作:
联合(Union) 交集(Intersection) 差集(Difference)
a | b # union
a & b # intersection
a ^ b # in a or in b but not in a & b equals a.symmetric_difference(b)
set的减法与被减数相关,等同set.difference(): all elements that are in this set but not the others.
>>m = set('arwb+tU') >>m set(['a', 'b', '+', 'r', 'U', 't', 'w']) >>set('r') - m set([]) # False >> set('2') - m set([2]) # True >>l = [1, 2, 3] >>ll = [2, 4, 6] >> set(l) - set(ll) set([2]) >> ll = [4, 6] >> set(l) - set(ll) set([1, 2, 3])
去掉 list 中的重复元素:
{}.fromkeys(list).keys() or set(list)
遍历
for i in alist: print i for index, item in enumerate(alist): print index, item
list 加法
alist = [2, 3] s = ["dfjo"]+alist >>s ['dfjo', 2, 3]