如何将一个numpy矩阵附加到一个空的numpy数组中 [英] how to append a numpy matrix into an empty numpy array

问题描述

我想通过循环将numpy数组(矩阵)附加到数组中

I want to append a numpy array(matrix) into an array through a loop

data=[[2 2 2] [3 3 3]]
Weights=[[4 4 4] [4 4 4] [4 4 4]]
All=np.array([])  
for i in data:
    #i=[2 2 2 ]  #for example
    h=i*Weights         
    #h=[[8 8 8][8 8 8][8 8 8]] 
    All=np.concatenate((All,h),axis=0)                

我会发生此错误:

ValueError: all the input arrays must have same number of dimensions

我希望"All"变量为

I want "All" variable to be

[[8 8 8][8 8 8][8 8 8] [12 12 12][12 12 12][12 12 12]]

如何通过循环将"h"添加到全部"?

Any way how I can add "h" to "All" through the loop ?

推荐答案

选项1 : 将初始的All数组重塑为3列，以使列数与h匹配:

Option 1: Reshape your initial All array to 3 columns so that the number of columns match h:

All=np.array([]).reshape((0,3))

for i in data:
    h=i*Weights      
    All=np.concatenate((All,h))

All
#array([[  8.,   8.,   8.],
#       [  8.,   8.,   8.],
#       [  8.,   8.,   8.],
#       [ 12.,  12.,  12.],
#       [ 12.,  12.,  12.],
#       [ 12.,  12.,  12.]])

选项2 : 使用if-else语句处理初始空数组情况:

Option 2: Use a if-else statement to handle initial empty array case:

All=np.array([])
for i in data:
    h=i*Weights      
    if len(All) == 0:
        All = h
    else:
        All=np.concatenate((All,h))

All
#array([[ 8,  8,  8],
#       [ 8,  8,  8],
#       [ 8,  8,  8],
#       [12, 12, 12],
#       [12, 12, 12],
#       [12, 12, 12]])

选项3 : 使用itertools.product():

import itertools
np.array([i*j for i,j in itertools.product(data, Weights)])

#array([[ 8,  8,  8],
#       [ 8,  8,  8],
#       [ 8,  8,  8],
#       [12, 12, 12],
#       [12, 12, 12],
#       [12, 12, 12]])

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