Pure Python Matrix Inverse

mtx_inv.py

def mtx_inv(M):
    I = mtx_idt(len(M))
    MI = [M[i]+I[i] for i in xrange(len(M))]
    for i in xrange(len(MI)):
        if MI[i][i] == 0:
            temp = M[i]
            M[i] = M[i+1]
            M[i+1] = temp
        if MI[i][i] != 1:
            h = MI[i][i]
            for j in xrange(len(MI[0])):
                MI[i][j] = Fraction(MI[i][j],h)
        for r in xrange(len(MI)):
            if r != i:
                h = MI[r][i]
                for c in xrange(len(MI[0])):
                    MI[r][c] -= h*MI[i][c]
        return [i[-len(M):] for i in MI]