Python code to generate the Hindu symbol Swastika of any given size

swastika.py

# generate a स्वस्तिक (swastika) of arm size n
# for n = 3
#        *     * * * *
#        *     *
#        *     *
#        * * * * * * *
#              *     *
#              *     *
#        * * * *     *

# For easily identifying the directions:
# "right": (0, 1),  # same row, next column
# "up": (-1, 0),  # previous row, same column
# "left": (0, -1),  # same row, previous column
# "down": (1, 0),  # next row, same column
def turn_right(current):
    return {
        (0, 1): (1, 0),  # right from right is down
        (-1, 0): (0, 1),  # right from up is right
        (0, -1): (-1, 0),  # right from left is up
        (1, 0): (0, -1),  # right from down is left
    }[current]


def swastika(size: int):
    m = [[" " for _ in range(2 * size + 1)] for _ in range(2 * size + 1)]
    if size < 0:
        return m
    m[size][size] = "*"
    directions = [(0, 1), (-1, 0), (0, -1), (1, 0)]  # right, up, left, down
    # get the deltas for: starting direction, then turn right direction
    for arm in [[d] * size + [turn_right(d)] * size for d in directions]:
        x0, y0 = size, size
        for dx, dy in arm:
            x0 += dx
            y0 += dy
            m[x0][y0] = "*"
    return m


def print_swastika(m):
    for row in m:
        print(" ".join(row))


swastika3 = """
*     * * * *
*     *      
*     *      
* * * * * * *
      *     *
      *     *
* * * *     *
""".strip().split("\n")

swastika2 = """
*   * * *
*   *    
* * * * *
    *   *
* * *   *
""".strip().split("\n")

assert [" ".join(line) for line in swastika(3)] == swastika3
assert [" ".join(line) for line in swastika(2)] == swastika2

print_swastika(swastika(3))
print_swastika(swastika(2))