Python如何遍历numpy数组

import numpy as np
num = np.zeros([2, 3])
[rows, cols] = num.shape
print(rows, cols)
for i in range(rows):
    for j in range(cols):
        print(num[i, j])

# 一维数组，和普通的python序列对象一致
>>> a
array([0, 1, 2, 3, 4])
>>> for i in a:
... print(i)
...
0
1
2
3
4
# 二维数组，每次遍历一行，以列表的形式返回一行的元素
>>> a = np.arange(12).reshape(3, 4)
>>> a
array([[ 0, 1, 2, 3],
       [ 4, 5, 6, 7],
       [ 8, 9, 10, 11]])
 
>>> for i in a:
... print(i)
...
[0 1 2 3]
[4 5 6 7]
[ 8 9 10 11]

>>> a
array([[ 0, 1, 2, 3],
       [ 4, 5, 6, 7],
       [ 8, 9, 10, 11]])
>>> for i in a.flat:
...     print(i)
...
0
1
2
3
4
5
6
7
8
9
10
11

>>> a
array([[ 0, 1, 2, 3],
       [ 4, 5, 6, 7],
       [ 8, 9, 10, 11]])
# 默认按行处理
>>> for i in np.nditer(a, order='C'):
... print(i)
...
0
1
2
3
4
5
6
7
8
9
10
11
# 按列处理
>>> for i in np.nditer(a, order='F'):
... print(i)
...
0
4
8
1
5
9
2
6
10
3
7
11

>>> a
array([[ 0, 1, 2, 3],
       [ 4, 5, 6, 7],
       [ 8, 9, 10, 11]])
>>> for i in np.nditer(a, op_flags = ['readwrite']):
... i *= 2
...
>>> a
array([[ 0, 2, 4, 6],
       [ 8, 10, 12, 14],
       [16, 18, 20, 22]])
 
>>> for i in np.nditer(a, op_flags = ['writeonly']):
... i += 2
...
>>> a
array([[ 2, 4, 6, 8],
       [10, 12, 14, 16],
       [18, 20, 22, 24]])

>>> a = np.arange(12).reshape(3, 4)
>>> a
array([[ 0, 1, 2, 3],
       [ 4, 5, 6, 7],
       [ 8, 9, 10, 11]])
>>> b = np.arange(4)
>>> b
array([0, 1, 2, 3])
>>> np.nditer([a, b])
<numpy.nditer object at 0x7f9db6b11170>
>>> for x,y in np.nditer([a,b]):
... print(x,y)
...
0 0
1 1
2 2
3 3
4 0
5 1
6 2
7 3
8 0
9 1
10 2
11 3
```
```
>>> b = np.arange(3).reshape(-1, 1)
>>> b
array([[0],
       [1],
       [2]])
>>> a
array([[ 0, 1, 2, 3],
       [ 4, 5, 6, 7],
       [ 8, 9, 10, 11]])
>>> for x,y in np.nditer([a,b]):
... print(x,y)
...
0 0
1 0
2 0
3 0
4 1
5 1
6 1
7 1
8 2
9 2
10 2
11 2