Question

I’m building a relatively simple programme to test collision detection, it’s all working fine at the moment except one thing, I’m trying to make the background colour change randomly, the only issue is that it appears to be completely skipping the function to do this;

import pygame from pygame.locals import * import random, math, time, sys pygame.init()  Surface = pygame.display.set_mode((800,600))  backgroundr = int(random.random()*255)+1 backgroundg = int(random.random()*255)+1 backgroundb = int(random.random()*255)+1  Circles = [] class Circle:     def __init__(self):         self.radius = int(random.random()*50) + 1         self.x = random.randint(self.radius, 800-self.radius)         self.y = random.randint(self.radius, 600-self.radius)         self.speedx = 0.5*(random.random()+1.0)         self.speedy = 0.5*(random.random()+1.0)         self.r = int(random.random()*255)+1         self.g = int(random.random()*255)+1         self.b = int(random.random()*255)+1 ##        self.mass = math.sqrt(self.radius)  for x in range(int(random.random()*30) + 1):     Circles.append(Circle())  def CircleCollide(C1,C2):     C1Speed = math.sqrt((C1.speedx**2)+(C1.speedy**2))     XDiff = -(C1.x-C2.x)     YDiff = -(C1.y-C2.y)     if XDiff > 0:         if YDiff > 0:             Angle = math.degrees(math.atan(YDiff/XDiff))             XSpeed = -C1Speed*math.cos(math.radians(Angle))             YSpeed = -C1Speed*math.sin(math.radians(Angle))         elif YDiff < 0:             Angle = math.degrees(math.atan(YDiff/XDiff))             XSpeed = -C1Speed*math.cos(math.radians(Angle))             YSpeed = -C1Speed*math.sin(math.radians(Angle))     elif XDiff < 0:         if YDiff > 0:             Angle = 180 + math.degrees(math.atan(YDiff/XDiff))             XSpeed = -C1Speed*math.cos(math.radians(Angle))             YSpeed = -C1Speed*math.sin(math.radians(Angle))         elif YDiff < 0:             Angle = -180 + math.degrees(math.atan(YDiff/XDiff))             XSpeed = -C1Speed*math.cos(math.radians(Angle))             YSpeed = -C1Speed*math.sin(math.radians(Angle))     elif XDiff == 0:         if YDiff > 0:             Angle = -90         else:             Angle = 90         XSpeed = C1Speed*math.cos(math.radians(Angle))         YSpeed = C1Speed*math.sin(math.radians(Angle))     elif YDiff == 0:         if XDiff < 0:             Angle = 0         else:             Angle = 180         XSpeed = C1Speed*math.cos(math.radians(Angle))         YSpeed = C1Speed*math.sin(math.radians(Angle))     C1.speedx = XSpeed     C1.speedy = YSpeed     C1.r = int(random.random()*255)+1     C1.g = int(random.random()*255)+1     C1.b = int(random.random()*255)+1     C2.r = int(random.random()*255)+1     C2.g = int(random.random()*255)+1     C2.b = int(random.random()*255)+1  def ColourCheck():     checknumber = int(random.random()*50)+1     if checknumber == 50:         backgroundr = int(random.random()*255)+1         backgroundg = int(random.random()*255)+1         backgroundb = int(random.random()*255)+1  def Move():     for Circle in Circles:         Circle.x += Circle.speedx         Circle.y += Circle.speedy def CollisionDetect():     for Circle in Circles:         if Circle.x < Circle.radius or Circle.x > 800-Circle.radius:             Circle.speedx *= -1             Circle.r = int(random.random()*255)+1             Circle.g = int(random.random()*255)+1             Circle.b = int(random.random()*255)+1         if Circle.y < Circle.radius or Circle.y > 600-Circle.radius:             Circle.speedy *= -1             Circle.r = int(random.random()*255)+1             Circle.g = int(random.random()*255)+1             Circle.b = int(random.random()*255)+1     for Circle in Circles:         for Circle2 in Circles:             if Circle != Circle2:                 if math.sqrt(  ((Circle.x-Circle2.x)**2)  +  ((Circle.y-Circle2.y)**2)  ) <= (Circle.radius+Circle2.radius):                     CircleCollide(Circle,Circle2) def Draw():     Surface.fill((backgroundr,backgroundg,backgroundb))     for Circle in Circles:         pygame.draw.circle(Surface,(Circle.r,Circle.g,Circle.b),(int(Circle.x),int(600-Circle.y)),Circle.radius)     pygame.display.flip()  def GetInput():     keystate = pygame.key.get_pressed()     for event in pygame.event.get():         if event.type == QUIT or keystate[K_ESCAPE]:             pygame.quit(); sys.exit()  def main():     while True:         ColourCheck()         GetInput()         Move()         CollisionDetect()         Draw() if __name__ == '__main__': main() 

it’s the ColourCheck function that’s being ignored, any ideas why?

Answer 1

I believe backgroundr, backgroundg, and backgroundb are local variables to your ColourCheck() function.

If you’re determined to use global variables, try this at the top of your file:

global backgroundr; global backgroundg; global backgroundb; backgroundr = int(random.random()*255)+1 backgroundg = int(random.random()*255)+1 backgroundb = int(random.random()*255)+1 

and this in your function:

def ColourCheck():     global backgroundr;     global backgroundg;     global backgroundb;     checknumber = int(random.random()*50)+1     if checknumber == 50:         backgroundr = int(random.random()*255)+1         backgroundg = int(random.random()*255)+1         backgroundb = int(random.random()*255)+1