Find neighbors of the matrix element at the given position

I force myself to learn something but before learning something new I need to memorize what I knew before. So I take python labs at exercism.org.

In one of the labs I had a chllange to find the neighour elements of the matrix element at the given position so I decided to save the solution for further refference.

For example given the matrix:

matrix = [
    "123",
    "456",
    "789"
]

I need to build the function that takes the the following arguments:

• matrix
• element position (x, y as a separate arguments)

The function should return all the elements arround the specified coordinates.

For example:

• if I specify x=0, y=1 that corrensponds with the “2” the function should return 1,3,4,5,6
• if I specify x=1, y=1 that corrensponds with the “5” the function should return 1,3,4,6,7,8,9

The logics is fairy simple:

• loop over rows in range x-1, x+2
• loop over columns in range y-1, y+2
• row index should be >0 and <len(row)
• column index should be >0 and <num(columns) or <len(row[0])
• exclude the element at specified position

def get_neighbors(matrix, x, y):
    num_rows, num_cols = len(matrix), len(matrix[0])
    
    for i in range( (0 if x-1 < 0 else x-1), (num_rows if x+2 > num_rows else x+2), 1  ):
        for j in range( (0 if y-1 < 0 else y-1), (num_cols if y+2 > num_cols else y+2), 1 ):
            if matrix[x][y] != matrix[i][j]:
                print(" • matrix["+str(i)+"]["+str(j)+"] = "+str(matrix[i][j]))

This example prints the values but it is possible to build the list() with the discovered values.

def get_neighbors(matrix, x, y):
    num_rows, num_cols = len(matrix), len(matrix[0])
    result =[]
    
    for i in range( (0 if x-1 < 0 else x-1), (num_rows if x+2 > num_rows else x+2), 1  ):
        for j in range( (0 if y-1 < 0 else y-1), (num_cols if y+2 > num_cols else y+2), 1 ):
            if matrix[x][y] != matrix[i][j]:
                result.append(matrix[i][j])
    return result

Another option is to build the dict() object using the discovered value as a key and cooridinates as a values.

def get_neighbors(matrix, x, y):
    num_rows, num_cols = len(matrix), len(matrix[0])
    result = dict()
    
    for i in range( (0 if x-1 < 0 else x-1), (num_rows if x+2 > num_rows else x+2), 1  ):
        for j in range( (0 if y-1 < 0 else y-1), (num_cols if y+2 > num_cols else y+2), 1 ):
            if matrix[x][y] != matrix[i][j]:
                result[matrix[i][j]] = [i,j]

    return result

Or you can do whatever modifications with the original mattrix you’d like to inside this function and return it as a result.