import numpy as np
a=[[1,2,3],[4,5,6],[7,8,9]]
a
[[1,2,3],[4,5,6],[7,8,9]]
type(a)
<type 'list'>
b=np.array(a)"""List to array conversion"""
type(b)
<type 'numpy.array'>
b
array=([[1,2,3],
    [4,5,6],
    [7,8,9]])

a[1][1]
5
a[1]
[4,5,6]
a[1][:]
[4,5,6]
a[1,1]"""相当于a[1,1]被认为是a[(1,1)],不支持元组索引"""
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: list indices must be integers, not tuple
a[:,1]
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: list indices must be integers, not tuple

b[1][1]
5
b[1]
array([4,5,6])
b[1][:]
array([4,5,6])
b[1,1]
5
b[:,1]
array([2,5,8])