import numpy as np

A = np.array([[-1, 0,0,0],[1,-1,0,0],[1,1,-1,0],[1,1,1,-1]])

print(A)

cond = np.linalg.cond(A)
print(cond)

B = np.diag(np.diag(A))
print(B)

C = A-B
print(C)

cond = np.linalg.cond(C)

print(cond)

inf