import numpy as np
import numpy.linalg as alg

A = np.array([[1,0],[0,2]])
B = np.array([[1,1],[1,1]])
C = np.array([[1,0],[0,-1]])

def det_mineur(A,k) :
    M = A[:k+1,:k+1]
    return alg.det(M)

def test(A) :
    n = A.shape[0]
    for k in range(n) :
        if det_mineur(A,k) <= 0 :
            return False
    return True