Getting TypeError: 'NoneType' object is not iterable error when extending two sliced list

Question

def rotLeft(a, d):
    rotate = a[:d]
    Remaining = a[d:]
    ar_rot=Remaining.extend(rotate)
    return ar_rot

我收到 ar_rot 变量的错误。为什么我在扩展两个时收到此错误 切片列表？类型错误：'NoneType' 对象不可迭代

Answer 1

因为 extend() return 什么都没有。尝试

def rotLeft(a, d):
    rotate = a[:d]
    Remaining = a[d:]
    Remaining.extend(rotate)
    return Remaining