# insert()append()delete()concatenate()hstack()vstack()等操作

<https://blog.csdn.net/weixin_37895339/article/details/78442555>

操作**不改变原数据，需要等式赋值**

## numpy.insert(arr,obj,value,axis=None)

value为插入的数值 arr:为目标向量 obj:为目标位置 value:为想要插入的数值 axis:为插入的维度

```python
#对a中,0维度,目标位1处，插入:[1,1,1,1]
a=np.insert(a,1,[1,1,1,1],0)
# a
array([[ 0,  1,  2,  3],
       [ 1,  1,  1,  1],
       [ 4,  5,  6,  7],
       [ 8,  9, 10, 11]])
```

## numpy.append(arr,values,axis=None)

与insert类似，只是append只是将values插入到目标arr的最后。 这里values跟arr应该为相同维度的向量。

## numpy.delete(arr,obj,axis=None)

arr:输入向量 obj:表明哪一个子向量应该被移除。可以为整数或一个int型的向量 axis:表明删除哪个轴的子向量，若默认，则返回一个被拉平的向量

## np.concatenate((a,b),axis=0)

```python
import numpy as np

a = np.array(np.arange(12).reshape(3, 4))
b = np.array(np.arange(12, 24).reshape(3, 4))

print(a)
print(b)
c=np.concatenate((a,b),axis=0)
print()
print(c)
'''
a: [[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]]
b: [[12 13 14 15]
 [16 17 18 19]
 [20 21 22 23]]
c: [[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]
 [12 13 14 15]
 [16 17 18 19]
 [20 21 22 23]]
'''
```

## hstack()水平堆叠

```python
a=[1,2,3] b=[4,5,6] 
print(np.hstack((a,b))) 
输出：[1 2 3 4 5 6 ]
```

## vstack()垂直堆叠

```python
a=[1,2,3]
b=[4,5,6]
print(np.vstack((a,b)))

输出：
[[1 2 3]
 [4 5 6]]
```


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