numpy concatenate数组拼接方法示例介绍

> import numpy as np
> a=np.array([1,2,5])
> b=np.array([10,12,15])
> a_list=list(a)
> b_list=list(b)

> a_list.extend(b_list)

> a_list
[1, 2, 5, 10, 12, 15]
> a=np.array(a_list)
> a
array([ 1, 2, 5, 10, 12, 15])

> a=np.arange(5)
> a
array([0, 1, 2, 3, 4])
> np.append(a,10)
array([ 0, 1, 2, 3, 4, 10])
> a
array([0, 1, 2, 3, 4])

 

> b=np.array([11,22,33])
> b
array([11, 22, 33])
> np.append(a,b)
array([ 0, 1, 2, 3, 4, 11, 22, 33])

 

> a
array([[1, 2, 3],
    [4, 5, 6]])
> b=np.array([[7,8,9],[10,11,12]])
> b
array([[ 7, 8, 9],
    [10, 11, 12]])
> np.append(a,b)
array([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12])

> a=np.array([1,2,3])
> b=np.array([11,22,33])
> c=np.array([44,55,66])
> np.concatenate((a,b,c),axis=0) # 默认情况下，axis=0可以不写
array([ 1, 2, 3, 11, 22, 33, 44, 55, 66]) #对于一维数组拼接，axis的值不影响最后的结果

 

> a=np.array([[1,2,3],[4,5,6]])
> b=np.array([[11,21,31],[7,8,9]])
> np.concatenate((a,b),axis=0)
array([[ 1, 2, 3],
    [ 4, 5, 6],
    [11, 21, 31],
    [ 7, 8, 9]])

> np.concatenate((a,b),axis=1) #axis=1表示对应行的数组进行拼接
array([[ 1, 2, 3, 11, 21, 31],
    [ 4, 5, 6, 7, 8, 9]])

> from time import clock as now
> a=np.arange(9999)
> b=np.arange(9999)
> time1=now()
> c=np.append(a,b)
> time2=now()
> print time2-time1
28.2316728446
> a=np.arange(9999)
> b=np.arange(9999)
> time1=now()
> c=np.concatenate((a,b),axis=0)
> time2=now()
> print time2-time1
20.3934997107

import numpy as np

a = np.array([[1, 2], [3, 4]])

a.shape
Out[3]: (2, 2)

b = np.array([[5, 6]])

b.shape
Out[5]: (1, 2)

np.concatenate((a, b))
Out[6]: 
array([[1, 2],
    [3, 4],
    [5, 6]])

c= np.concatenate((a, b))

c.shape
Out[8]: (3, 2)

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

d.shape
Out[10]: (3, 2)

e = np.concatenate((a, b), axis=1)
Traceback (most recent call last):

 File "<ipython-input-11-05a280a2cb02>", line 1, in <module>
  e = np.concatenate((a, b), axis=1)

ValueError: all the input array dimensions except for the concatenation axis must match exactly


e = np.concatenate((a, b.T), axis=1)

e.shape
Out[13]: (2, 3)


import numpy as np
a = np.array([[1, 2], [3, 4]])
a.shape
Out[3]: (2, 2)
b = np.array([[5, 6]])
b.shape
Out[5]: (1, 2)
np.concatenate((a, b))
Out[6]: 
array([[1, 2],
    [3, 4],
    [5, 6]])
c= np.concatenate((a, b))
c.shape
Out[8]: (3, 2)
d = np.concatenate((a, b), axis=0)
d.shape
Out[10]: (3, 2)
e = np.concatenate((a, b), axis=1)
Traceback (most recent call last):
 File "<ipython-input-11-05a280a2cb02>", line 1, in <module>
  e = np.concatenate((a, b), axis=1)
ValueError: all the input array dimensions except for the concatenation axis must match exactly

e = np.concatenate((a, b.T), axis=1)
e.shape
Out[13]: (2, 3)