fixed flickering while rendering chessboard

board.py

@@ -1,19 +1,10 @@
 import pygame as pg    
 
-def render_board():
+def render_board(screen, size):
     
-    size = 900
-
-    #start pygame
-    pg.init()
-    screen = pg.display.set_mode((size, size)) #window (size)
-    
-
     color = (255, 255, 255)    #rectangle color
     sizeW = size / 8    #rectangle size
     sizeH = size / 8    #rectangle size
-    
-    
     posX, posY = 0, 0   #recatangle position x, recatangle position y
     s1 = True           #wether or not the first square of the row should be black or white
 

main.py

@@ -13,16 +13,17 @@ line1 = [p4, p3, p2, p5, p6, p2, p3, p4]
 line2 = [p1, p1, p1, p1, p1, p1, p1, p1]
 
 pg.init()
+size = 900
+screen = pg.display.set_mode((size, size))
 clock = pg.time.Clock()
 running = True
 
 while running:      #open window
-
     for event in pg.event.get():
         if event.type == pg.QUIT:
             running = False
     
-    render_board()
+    render_board(screen, size)
 
     #flip display to put game on screen
     pg.display.flip()