How to create a for loop to process a multid-dimensional matrix in Python

Question

Assume I have a four-dimensional matrix A(:, :, :, :). I want to update the matrix by performing some processing on it. The pseudo codes are presented as follows:

for ii = 1:m
 for jj = 1:n
 A = myFunction(A(:,:,jj,ii))
 end
end

To implement the for-loop processing in Python:

for ii in range(m):
 for jj in range(n):
 A = myFunction(A[:,:,jj,ii])

Is that correct?

• Barmar: To process an n-dimensional array, you need n nested loops.
• jwm: can you show the code to realize the 4-D matrix?
• Barmar: it's the same as for 2-D, just add loops for kk and ll.
• rnbguy: for multi-dimension matrix and these kind of loops, ndarray from numpy would be best choice.
• jwm: You mean the code structure is valid in Python? It seems I need to make the index range from 0 to max-1 and delete the two 'end' . I am new to Python programming.

Answer 1

If you have 4-dimensional matrix, you should use 4 indexes:

for i in range(m):
 for j in range(n):
 for k in range(p):
 for l in range(q):
 myFunction(A[i,j,k,l])

For example:

A = [[[[6,1],[4,3]],[[4,8],[0,9]]],[[[1,5],[3,9]],[[5,5],[2,7]]]]
s = 0
for i in range(2):
 for j in range(2):
 for k in range(2):
 for l in range(2):
 s += A[i][j][k][l]
print(s)