[Python] Find neighbors in a matrix?

Here is a 7x7 matrix:

11 21 31 41 51 61 71
12 22 32 42 52 62 72
13 23 33 43 53 63 73
14 24 34 44 54 64 74
15 25 35 45 55 65 75
16 26 36 46 56 66 76
17 27 37 47 57 67 77


The numbers 11, 21, 33 … are the values of the positions. If a radius, the number of row and the number of column are given, how to find the neighbors?

For example, function neighbors(radius = 1, rowNumber = 3, columnNumber = 3) should return a matrix:

22 32 42
23 33 43
24 34 44


function neighbors(radius = 2, rowNumber = 3, columnNumber = 3) should return a matrix:

11 21 31 41 51
12 22 32 42 52
13 23 33 43 53
14 24 34 44 54
15 25 35 45 55


When the neighbor is out of boundary, its value should be 0. For example, function neighbors(radius = 2, rowNumber = 1, columnNumber = 1) should return a matrix

0 0 0 0 0
0 0 0 0 0
0 0 11 21 31
0 0 12 22 32
0 0 13 23 33


I've been thing about this problem for 3 days, but I still can't develop a solution for it.

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