extmath.py 文件源码

def norm(x):
    """Compute the Euclidean or Frobenius norm of x.

    Returns the Euclidean norm when x is a vector, the Frobenius norm when x
    is a matrix (2-d array). More precise than sqrt(squared_norm(x)).
    """
    x = np.asarray(x)
    nrm2, = linalg.get_blas_funcs(['nrm2'], [x])
    return nrm2(x)


# Newer NumPy has a ravel that needs less copying.