我想制作一个列表,从末尾开始将其元素乘以 2,步长为 -2。例如:
a = [1, 2, 3, 4, 5, 6, 7]
# I want it to return a = [2, 2, 6, 4, 10, 6, 14]
我有一些想法,但我尝试的都不起作用。看看我的代码:
a = [1, 2, 3, 4, 5, 6, 7]
a = [i*2 for i in a[-1::-2]]
print(a)
#or
a = [1, 2, 3, 4, 5, 6, 7]
for i in a[-1::-2]:
i *= 2
#returns only 14, 10, 6, 2
使用模除法:
a = [1, 2, 3, 4, 5, 6, 7]
res = [n * 2 if i % 2 == 0 else n for i, n in enumerate(a)]
print(res)
[2, 2, 6, 4, 10, 6, 14]
你的逻辑几乎是正确的。在 indices 上循环并分配回列表:
a = [1, 2, 3, 4, 5, 6, 7]
for i in range(len(a)-1, -1, -2):
a[i] *= 2
输出:
[2, 2, 6, 4, 10, 6, 14]