Creates a spiral of numbers in a matrix NxN

vortex.py

# creates a spiral of numbers in a matrix NxN

from copy import copy

def vortex(n):
    i = 1
    row = [0] * n
    matrix = [copy(row) for _ in range(n)]

    pos_row = 0
    pos_col = 0
    dir = 'right' # 'left', 'up', 'down'
    stop = False

    while not stop:
        matrix[pos_row][pos_col] = i
        i += 1
        if dir == 'right':
            if has_next(matrix, pos_row, pos_col, dir):
                pos_col += 1
                continue
            else:
                if has_next(matrix, pos_row, pos_col, 'down'):
                    dir = 'down'
                    pos_row += 1
                    continue
                else:
                    stop = True

        if dir == 'down':
            if has_next(matrix, pos_row, pos_col, dir):
                pos_row += 1
                continue
            else:
                if has_next(matrix, pos_row, pos_col, 'left'):
                    dir = 'left'
                    pos_col -= 1
                    continue
                else:
                    stop = True

        if dir == 'left':
            if has_next(matrix, pos_row, pos_col, dir):
                pos_col -= 1
                continue
            else:
                if has_next(matrix, pos_row, pos_col, 'up'):
                    dir = 'up'
                    pos_row -= 1
                    continue
                else:
                    stop = True

        if dir == 'up':
            if has_next(matrix, pos_row, pos_col, dir):
                pos_row -= 1
                continue
            else:
                if has_next(matrix, pos_row, pos_col, 'right'):
                    dir = 'right'
                    pos_col += 1
                    continue
                else:
                    stop = True
    return matrix

def has_next(matrix, pos_row, pos_col, dir):
    size = len(matrix)
    if dir == 'right':
        return pos_col+1 < size and matrix[pos_row][pos_col+1] == 0

    if dir == 'left':
        return pos_col-1 >= 0 and matrix[pos_row][pos_col-1] == 0

    if dir == 'down':
        return pos_row+1 < size and matrix[pos_row+1][pos_col] == 0

    if dir == 'up':
        return pos_row-1 >= 0 and matrix[pos_row-1][pos_col] == 0

    return None

assert vortex(1) == [[1]]
assert vortex(2) == [[1, 2], [4, 3]]
assert vortex(3) == [[1, 2, 3], [8, 9, 4], [7, 6, 5]]
assert vortex(4) == [[1, 2, 3, 4], [12, 13, 14, 5], [11, 16, 15, 6], [10, 9, 8, 7]]

for row in vortex(9):
    print(",".join(str(i).rjust(3) for i in row))