Infinite While Loop inside a For Loop

I am trying to implement the Mid-Point Circle Drawing Algorithm on OpenGL and PyCharm. My aim is to draw eight circles inside a bigger circle. The eight inner circles each belong to a zone inside the bigger circle. An illustration of the figure I am trying to generate is shown in the image.

In my code, I have used one function to draw the bigger circle and a separate function to draw the eight inner circles using the Mid-Point Circle Drawing Algorithm. In the function for the eight inner circles, I have taken a list of the four zones (for now) and used a for loop to traverse the list. For each iteration, the mid-point circle algorithm will be executed and generate a circle for that respective zone. But my program is showing only one inner circle after running it. My while-loop is running infinitely, hence, the outer for loop is stuck in its first iteration. How can I address this and make my code work?

**NOTE: For simplicity, I am trying to make it work for four zones now. Hence, the length of my list is four for now. **

from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.GLU import *

def circle_points(x, y, centre_x, centre_y,):

    glVertex2f(x + centre_x, y + centre_y)
    glVertex2f(x + centre_x, -y + centre_y)
    glVertex2f(-x + centre_x, y + centre_y)
    glVertex2f(-x + centre_x, -y + centre_y)
    glVertex2f(y + centre_x, x + centre_y)
    glVertex2f(y + centre_x, -x + centre_y)
    glVertex2f(-y + centre_x, -x + centre_y)
    glVertex2f(-y + centre_x, x + centre_y)



# function for bigger circle
def draw_circle(r):
    glPointSize(2)
    glBegin(GL_POINTS)
    glColor3f(1.0,1.0,1.0)

    x = 0
    y = r
    d = 1 - r  #decision parameter
    centre_x, centre_y = 250, 250  #taking centre of the circle


    while x <= y:
        circle_points(x, y, centre_x, centre_y)
        if d >= 0:
            d = d + 2*(x-y)+1
            x = x+1
            y = y-1
        else:
            d = d + 2*x+1
            x = x + 1



    glEnd()

# function for inner circles
def draw_inner_circles(r):
    glPointSize(2)
    glBegin(GL_POINTS)
    glColor3f(1.0, 1.0, 1.0)

    x = 0
    y = r
    d = 1 - r  # decision parameter



    zones = ['1','2','3','4']
    for i in zones:
        centre_x, centre_y = 250, 250
        if i == '1':
            centre_x = centre_x
            centre_y = centre_y + r
        elif i == '2':
            centre_x = centre_x
            centre_y = centre_y - r
        elif i == '3':
            centre_x = centre_x + r
            centre_y = centre_y

        elif i == '4':
            center_x = centre_x - r
            centre_y = centre_y
        while x <= y:
            circle_points(x, y, centre_x, centre_y)

            if d >= 0:
                d = d + 2 * (x - y) + 1
                x = x + 1
                y = y - 1
            else:
                d = d + 2 * x + 1
                x = x + 1



    glEnd()












def iterate():
    glViewport(0, 0, 500, 500)
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    glOrtho(0.0, 500, 0.0, 500, 0.0, 1.0)
    glMatrixMode (GL_MODELVIEW)
    glLoadIdentity()


def showScreen():
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glLoadIdentity()
    iterate()
    glColor3f(1.0, 1.0, 1.0)
    # funtion call 
    draw_circle(200)
    draw_inner_circles(100)

    glutSwapBuffers()






glutInit()
glutInitDisplayMode(GLUT_RGBA)
glutInitWindowSize(500, 500) #window size
glutInitWindowPosition(0, 0)
wind = glutCreateWindow(b"OpenGL Coding Practice") #window name
glutDisplayFunc(showScreen)


glutMainLoop()

>Solution :

Are you sure the while loop is running infinitely? It seems like when the first inner circle is drawn, thus x > y, you never reset the x and y, so it never gets to run the while loop for the other iterations. Try with something like this:

    zones = ['1','2','3','4']
    for i in zones:
        centre_x, centre_y = 250, 250
        if i == '1':
            centre_x = centre_x
            centre_y = centre_y + r
        elif i == '2':
            centre_x = centre_x
            centre_y = centre_y - r
        elif i == '3':
            centre_x = centre_x + r
            centre_y = centre_y

        elif i == '4':
            center_x = centre_x - r
            centre_y = centre_y
       
        x = 0
        y = r
        d = 1 - r  # decision parameter
        while x <= y:
            circle_points(x, y, centre_x, centre_y)
            if d >= 0:
                d = d + 2 * (x - y) + 1
                x = x + 1
                y = y - 1
            else:
                d = d + 2 * x + 1
                x = x + 1