如何在不使用 NumPy 的情况下在单独的行中打印列表中的两个输入列表？

Question

I have a program which adds two matrices (lists) and prints the sum. First, the program asks to specify the number of rows and columns as dimensions of the matrices.

Then it asks to enter the specified number of digits as rows and columns, as follows:

dimension:              2 3
numbers in the list:    1 2 3
numbers in the list:    4 5 6

dimension:              2 3
numbers in the list:    7 8 9
numbers in the list:    7 8 9

I am trying to print the sum of two input lists (matrices) exactly in the following format - two rows in separate lines, three columns, without square brackets:

8 10 12
11 13 15

but end up with this output:

[8, 11, 10, 13, 12, 15]

I have tried several other solutions suggested in other similar posts but haven't been able to make them work.

Without using NumPy , map() or lambda functions, how can I get the desired output?

# input the number of rows and columns (dimensions of the matrix)
rows_cols = input().split()

# save the dimensions as integers in a list
matrix_dim = [int(i) for i in rows_cols]

numbers = 0
matrix_A = []
matrix_B = []
matrices = []

# take the row times the input for the rows of matrix_A
for _ in range(matrix_dim[0]):
    numbers = input().split()
    matrix_A.append([int(i) for i in numbers])
rows_cols = input().split()
matrix_dim = [int(i) for i in rows_cols]

# take the row times the input for the rows of matrix_B
for _ in range(matrix_dim[0]):
    numbers = input().split()
    matrix_B.append([int(i) for i in numbers])

# add matrices matrix_A and matrix_B
matrices = [matrix_A[i][k] + matrix_B[i][k] for k in range(len(matrix_A[0])) for i in range(len(matrix_A))]

# print ERROR if the number of columns entered exceed the input number for columns
if len(numbers) != matrix_dim[1]:
    print("ERROR")
else:
    print(matrices)

Answer 1

All you have to do is change how you sum the matrices:

matrices = [[matrix_A[i][k] + matrix_B[i][k] for k in range(len(Matrix_A[0]))] for i in range(len(matrix_A))]

Then to print:

for row in matrices:
    # print(row)
    print(" ".join(row))

Or

from pprint import pprint

pprint(matrices)

Answer 2

The easy way to do this will be to start with the fix suggested by nathan:

matrices = [[matrix_A[i][k] + matrix_B[i][k] for k in range(len(Matrix_A[0]))] for i in range(len(matrix_A))]

That gives you a 2-d array rather than a 1-d array

[[a, b, c], [d, e, f]]

but now we need to print it nicely. Here's a function to turn the matrix into a pretty string:

def prettyString(matrix):
  result = ''
  for row in matrix:
    for value in row:
      result += value
    result += '\n'
  return result

Finally, in your code, you can use the new function:

print(prettyString(matrices))

Answer 3

Try this -

First calculate the sum list of lists as output, then join the elements of sublist with spaces and join those sublists strings with \\n (newline character). When you then print it, it will print it out one sublist at a time.

output = [[a[i][j] + b[i][j] for j in range(len(a[0]))] for i in range(len(a))]

print_out = '\n'.join([' '.join([str(j) for j in i]) for i in output])

print(print_out)

#sample output
1 2 3
4 5 6

Answer 4

zip function can be helpful when you try to combine lists of lists. This will work for any nxm matrices.

m1 = [
[1,2,3],
[4,5,6]]

m2 = [
[7,8,9],
[7,8,9]]

for row1,row2 in zip(m1,m2):
    print(*[el1+el2 for el1,el2 in zip(row1,row2)])

Output:

8 10 12
11 13 15