Unit 1, Mandelbrot (Python, v2)

# Limit for maximum iterations
MAX_ITER = 256
SYMBOLS = ".:coCO8@"


height = input("Enter size of the fractal (height and width)\n")
width = input()

for y in range(height):
    line = []

    for x in range(width):
        x0 = (3.5 / width) * x - 2.5
        y0 = (2.0 / height) * y - 1
        xi = yi = 0.0
        iteration = 0

        while xi*xi + yi*yi < 4 and iteration < MAX_ITER:
            xtemp = xi*xi - yi*yi + x0
            yi = 2*xi*yi + y0
            xi = xtemp
            iteration += 1

        if (iteration == MAX_ITER):
            line.append(" ")
        else:
            line.append(SYMBOLS[(iteration - 1) % 8])

    print "".join(line)