I was wondering if there is any function in numpy to determine whether a matrix is Unitary?

This is the function I wrote but it is not working. I would be thankful if you guys can find an error in my function and/or tell me another way to find out if a given matrix is unitary.

def is_unitary(matrix: np.ndarray) -> bool:unitary = Truen = matrix.sizeerror = np.linalg.norm(np.eye(n) - matrix.dot( matrix.transpose().conjugate()))if not(error < np.finfo(matrix.dtype).eps * 10.0 *n):unitary = Falsereturn unitary

Let's take an obviously unitary array:

>>> a = 0.7
>>> b = (1-a**2)**0.5
>>> m = np.array([[a,b],[-b,a]])
>>> m.dot(m.conj().T)
array([[ 1.,  0.],[ 0.,  1.]])

and try your function on it:

>>> is_unitary(m)
Traceback (most recent call last):File "<ipython-input-28-8dc9ddb462bc>", line 1, in <module>is_unitary(m)File "<ipython-input-20-3758c2016b67>", line 5, in is_unitaryerror = np.linalg.norm(np.eye(n) - matrix.dot( matrix.transpose().conjugate()))
ValueError: operands could not be broadcast together with shapes (4,4) (2,2) 

which happens because

>>> m.size
4
>>> np.eye(m.size)
array([[ 1.,  0.,  0.,  0.],[ 0.,  1.,  0.,  0.],[ 0.,  0.,  1.,  0.],[ 0.,  0.,  0.,  1.]])

If we replace n = matrix.size with len(m) or m.shape[0] or something, we get

>>> is_unitary(m)
True

I might just use

>>> np.allclose(np.eye(len(m)), m.dot(m.T.conj()))
True

where allclose has rtol and atol parameters.