python3 整数的list,可以用一个list把某一个元素覆盖掉

import numpy as np
a=[np.nan]*10
a
[nan, nan, nan, nan, nan, nan, nan, nan, nan, nan]

a[0]=[1,3,4]
a
[[1, 3, 4], nan, nan, nan, nan, nan, nan, nan, nan, nan]

b=[1]*10
b
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1]

b[0]=[1,23,4]
b
[[1, 23, 4], 1, 1, 1, 1, 1, 1, 1, 1, 1]