Python fill in elements of large matrix with same value

Python fill in elements of large matrix with same value
python
Ethan Jackson

I have a large matrix where I want to assign the same value(s) to many matrix elements. Is there a more efficient way to do this rather than iterating over each column and row using for loops? Here is a MWE:

import numpy as np a = 0.5 b = 0.6 M = np.zeros((16,16)) # empty matrix np.fill_diagonal(M, 0.9) # diagonal elements for jj in range(0,16): # rows for kk in range(0,16): # columns if jj == 0: if (kk == 1) | (kk == 3): M[jj,kk] = a if jj == 3: if (kk == 0) | (kk == 2): M[jj,kk] = b if jj == 5: if (kk == 4) | (kk == 6): M[jj,kk] = a # etc print(M)

Answer

A possible solution:

idxr_a = [0, 0, 5, 5] # row index idxc_a = [1, 3, 4, 6] # col index M[idxr_a, idxc_a] = a idxr_b = [3, 3] # row index idxc_b = [0, 2] # col index M[idxr_b, idxc_b] = b

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