How to create a comparision matrix using python-CodePudding

i have list in python how can i generate a matrix by subtracting the list element by each othe and create a comaprision matrix and save it into csv

list_a = [1,2,4]
list_b = [1,2,4]

for i in list_a:
    for j in list_b:
        print(i - j)


i want to write its output like matrix  [0    1    3 ]
                                        [-1   0    2 ]
                                        [-3   -2   0 ]

CodePudding user response：

you can transpose the list of list using map and zip

list_a = [1,2,4]
list_b = [1,2,4]

matrix_output = []

for i in list_a:
    matrix_output.append([])
    for j in list_b:
        matrix_output[-1].append(i-j)
    
matrix_output_transposed = list(map(list, zip(*matrix_output)))
for cell in matrix_output_transposed:
    print(cell)

CodePudding user response：

if u use numpy, then it is most easiest solution. following snip generates expected results. please check once

import numpy as np
list_a = [1,2,4]
list_b = [1,2,4]
y = np.subtract.outer(np.array(list_a), np.array(list_b)).T
print(y)