Python合并两个List

1.使用list的extend()方法，现有两个list分别为L1和L2：

1 >>> L1 = [1, 2, 3, 4, 5]
2 >>> L2 = [20, 30, 40]
3 >>> L1.extend(L2)
4 >>> L1
5 [1, 2, 3, 4, 5, 20, 30, 40]

2.用切片(slice)操作，L1[len(L1):len(L1)] = L2和上面的方法等价，例如：

1 >>> L1 = [1, 2, 3, 4, 5]
2 >>> L2 = [20, 30, 40]
3 >>> L1[len(L1):len(L1)] = L2
4 >>> 
5 >>> L1
6 [1, 2, 3, 4, 5, 20, 30, 40]

用切片方法的好处在于灵活，可以在任意节点进行插入，例如从头部插入：

1 >>> L1 = [1, 2, 3, 4, 5]
2 >>> L2 = [20, 30, 40]
3 >>> L1[0:0] = L2
4 >>> L1
5 [20, 30, 40, 1, 2, 3, 4, 5]

例如加到中间：

1 >>> L1 = [1, 2, 3, 4, 5]
2 >>> L2 = [20, 30, 40]
3 >>> 
4 >>> L1[1:1] = L2
5 >>> L1
6 [1, 20, 30, 40, 2, 3, 4, 5]