用Python中的相同列表减去列表中的列表

Question

I have a list as below:

A=[[1,2,3],[4,5,6],[7,8,9]]

Now I would like to subtract all the lists in A with B

B=[1,1,1]

to get the following result C:

C=[[0,1,2],[3,4,5],[6,7,8]]

I know I can use zip to do two list subtraction, but I cannot use it directly on list within list. How can I do the above subtraction? Thanks

Answer 1

Using a list comprehension with zip :

C = [[a-b for a, b in zip(sublist, B)] for sublist in A]

Alternatively, using a list comprehension with enumerate :

C = [[j-B[i] for i, j in enumerate(sublist)] for sublist in A]

Using 3rd party library NumPy, you can utilize broadcasting to output an array:

import numpy as np

A = np.array([[1,2,3],[4,5,6],[7,8,9]])
B = np.array([1,1,1])

C = A - B

print(C)

array([[0, 1, 2],
       [3, 4, 5],
       [6, 7, 8]])

Answer 2

Using numpy .

Demo:

import numpy as np
A=[[1,2,3],[4,5,6],[7,8,9]]
B=[1,1,1]
C = [list(np.array(i) - np.array(B)) for i in A]
print(C)

Using operator.sub

from operator import sub
A=[[1,2,3],[4,5,6],[7,8,9]]
B=[1,1,1]
C = [list(map(sub, i, B)) for i in A]
print(C)

Output:

[[0, 1, 2], [3, 4, 5], [6, 7, 8]]

Answer 3

import operator
A=[[1,2,3],[4,5,6],[7,8,9]]B=[1,1,1]
B=[1,1,1]
C=[list(map(operator.sub, i,B)) for i in A]
print C

Answer 4

Here is an alternative approach without the use of NUMPY -

for innerList in A:
    newInner = []
    for j in range(0, len(innerList)):
        newInner.append(innerList[j] - B[j])
    C.append(newInner)