[Python] Shrink a matrix (i.e. remove borders lines filled with 0)

Using NumPy and according a matrix is equal to an array …
I want to shrink a matrix.
I mean by that remove all the borders empty lines (filled with 0)
Example:
Matrix to shrink:

array([[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 0, 1, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 0, 1, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0]], dtype=uint8)


Result expected:

array([[1, 0, 1],
[0, 0, 0],
[1, 0, 1]], dtype=uint8)


To do that, I wrote this function:

import numpy as np

def shrink(mat):
while mat[0].any()==0 or mat[-1].any()==0 or mat[:,0].any()==0 or mat[:,-1].any()==0:
if mat[0].any()==0:
mat = np.delete(mat, 0, 0)
if mat[-1].any()==0:
mat = np.delete(mat, -1, 0)
if mat[:,0].any()==0:
mat = np.delete(mat, 0, 1)
if mat[:,-1].any()==0:
mat = np.delete(mat,-1, 1)
return mat


It works but I'm pretty sure there is a better method …

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