python - 编写一个函数，该函数接受一个列表作为参数，并返回一个复制列表中元素的 LIST

Question

我正在尝试编写一个函数，该函数接受输入，例如 [1, 2, 3] 并返回 [1, 1, 2, 2, 3, 3]，但出现错误

这是我现在的代码

def problem3(aList):
    list1= []
    newList1= []
    for i in range (len(aList)):
        list1.append(aList[i])
    for i in range (0, len(list1)):
        newList1= aList + list1[i]

这是错误

"Traceback (most recent call last): Python Shell, prompt 2, line 1 File "h:\TowlertonEvanDA7.py", line 34, in newList1= aList + list1[i] builtins.TypeError: can only concatenate list (not "int") to list"

Answer 1

你可以这样做:

def problem3(aList):
    newList1= []
    for i in aList:
        newList1.extend((i, i))
    return newList1

lst = [1,2,3]
print problem3(lst)

# [1, 1, 2, 2, 3, 3]