Local variable being referenced before assignment; can't work out why

Question

I have this task for uni. I've changed my code around over 3 times now and even adapted it to a working one. We have two modes: one where ghosts bounce off Pac-Man and the other where Pac-Man bounces off them. I know I could use lists to shorten this code but I'm still learning how to make them work right.

I get this error every time without fail and I really have no clue why so any advice would be great.

Traceback (most recent call last):
  File "C:/", line 111, in <module>
    mode_switch()
  File "C:/", line 21, in mode_switch
    blue_right, orange_right, pink_right,\
UnboundLocalError: local variable 'blue_right' referenced before assignment

My code

import pygame


import pygame
from random import *



pygame.init()

def ghost_collision():

    SCREAM.play()
    pacman_velocity[0] = randint(-1,1)
    pacman_velocity[1] = randint(-1,1)
    if pacman_velocity[0] < 0:
        pacman = pygame.image.load(PACMAN_LEFT).convert()
    elif pacman_velocity[0] > 0:
        pacman = pygame.image.load(PACMAN_RIGHT).convert()
    return pacman_velocity

def mode_switch():
    global mode
    blue_right, orange_right, pink_right,\
          red_right, blue, orange, pink, red
    if mode == False:
        mode = True
        blue = pygame.image.load(GHOST_SCARED).convert()
        orange = pygame.image.load(GHOST_SCARED).convert()
        pink = pygame.image.load(GHOST_SCARED).convert()
        red = pygame.image.load(GHOST_SCARED).convert()
    else:
        mode = False
        if blue_right == True:
            blue = pygame.image.load(BLUE_LEFT).convert()
            blue_right = False
        else:
            blue = pygame.image.load(BLUE_RIGHT).convert()
            blue_right = True
    if orange_right == True:
        orange = pygame.image.load(ORANGE_LEFT).convert()
        orange_right = False
    else:
        orange = pygame.image.load(ORANGE_RIGHT).convert()
        orange_right = True
    if pink_right == True:
        pink = pygame.image.load(PINK_LEFT).convert()
        pink_right = False
    else:
        pink = pygame.image.load(PINK_RIGHT).convert()
        pink_right = True
    if red_right == True:
        red = pygame.image.load(RED_LEFT).convert()
        red_right = False
    else:
        red = pygame.image.load(RED_RIGHT).convert()
        red_right = True


PACMAN_LEFT = 'pacman-left.png'
PACMAN_RIGHT = 'pacman-right.png'
BLUE_LEFT = 'blue-left.png'
BLUE_RIGHT = 'blue-right.png'
ORANGE_LEFT = 'orange-left.png'
ORANGE_RIGHT = 'orange-right.png'
PINK_LEFT = 'pink-left.png'
PINK_RIGHT = 'pink-right.png'
RED_LEFT = 'red-left.png'
RED_RIGHT = 'red-right.png'
GHOST_SCARED = 'vulnerable.png'
BOUNCE_SOUND = 'Thump.wav'
SOUND = pygame.mixer.Sound(BOUNCE_SOUND)
WIDTH = 800
HEIGHT = 600
BACKGROUND_COLOUR = 0, 0, 0
CAPTION = 'Random Pacman'
pacman_up = True#define image direction controlling variables
pacman_right = True
blue_right = False
orange_right = True
pink_right = False
red_right = True
mode = False

frame = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption(CAPTION)
pacman = pygame.image.load(PACMAN_RIGHT).convert()#create sprites and define boundaries
pacman_boundary = pacman.get_rect(center = (300,300))
pacman_velocity = [1, 1]
blue = pygame.image.load(BLUE_LEFT).convert()
blue_boundary = pacman.get_rect(center = (300,300))
blue_velocity = [-1, -1]
orange = pygame.image.load(ORANGE_RIGHT).convert()
orange_boundary = pacman.get_rect(center = (300,300))
orange_velocity = [1, -1]
pink = pygame.image.load(PINK_LEFT).convert()
pink_boundary = pacman.get_rect(center = (300,300))
pink_velocity = [-1, 1]
red = pygame.image.load(RED_RIGHT).convert()
red_boundary = pacman.get_rect(center = (300,300))
red_velocity = [1, 1]

finished = False
while not finished:
    pygame.event.pump()
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            finished = True
        if event.type == pygame.MOUSEBUTTONUP:
            mode_switch()

    #####################################################

if pacman_boundary.left < 0 or pacman_boundary.right > WIDTH:
    SOUND.play()
    pacman_velocity[0] = -1 * pacman_velocity[0]
    if pacman_velocity[0] < 0:
        pacman = pygame.image.load(PACMAN_LEFT).convert()
    elif pacman_velocity[0] > 0:
        pacman = pygame.image.load(PACMAN_RIGHT).convert()
    pacman_velocity[1] = randint(-1,1)

if pacman_boundary.top < 0 or pacman_boundary.bottom > HEIGHT:
    SOUND.play()
    pacman_velocity[1] = -1 * pacman_velocity[1]

if mode == False:        
    if pacman_boundary.colliderect(blue_boundary)\
       or pacman_boundary.colliderect(orange_boundary)\
       or pacman_boundary.colliderect(pink_boundary)\
       or pacman_boundary.colliderect(red_boundary):
        ghost_collision()

    #####################################################

if blue_boundary.left < 0 or blue_boundary.right > WIDTH:
    blue_velocity[0] = -1 * blue_velocity[0]
    if mode == False:
        if blue_right == True:
            blue = pygame.image.load(BLUE_LEFT).convert()
            blue_right = False
        else:
            blue = pygame.image.load(BLUE_RIGHT).convert()
            blue_right = True

if blue_boundary.top < 0 or blue_boundary.bottom > HEIGHT:
    SOUND.play()
    blue_velocity[1] = -1 * blue_velocity[1]

if mode == True:
    if pacman_boundary.colliderect(blue_boundary):

        blue_velocity[0] = randint(-1,1)
        blue_velocity[1] = randint(-1,1)



#####################################################

if orange_boundary.left < 0 or orange_boundary.right > WIDTH:
    orange_velocity[0] = -1 * orange_velocity[0]
    if mode == False:
        if orange_right == True:
            orange = pygame.image.load(ORANGE_LEFT).convert()
            orange_right = False
        else:
            orange = pygame.image.load(ORANGE_RIGHT).convert()
            orange_right = True

if orange_boundary.top < 0 or orange_boundary.bottom > HEIGHT:
    SOUND.play()
    orange_velocity[1] = -1 * orange_velocity[1]

if mode == True:
    if pacman_boundary.colliderect(orange_boundary):
        orange_velocity[0] = randint(-1,1)
        orange_velocity[1] = randint(-1,1)


#####################################################

if pink_boundary.left < 0 or pink_boundary.right > WIDTH:#
    pink_velocity[0] = -1 * pink_velocity[0]
    if mode == False:
        if pink_right == True:
            pink = pygame.image.load(PINK_LEFT).convert()
            pink_right = False
        else:
            pink = pygame.image.load(PINK_RIGHT).convert()
            pink_right = True

if pink_boundary.top < 0 or pink_boundary.bottom > HEIGHT:
    SOUND.play()
    pink_velocity[1] = -1 * pink_velocity[1]

if mode == True:
    if pacman_boundary.colliderect(pink_boundary):
        pink_velocity[0] = randint(-1,1)
        pink_velocity[1] = randint(-1,1)


#####################################################

if red_boundary.left < 0 or red_boundary.right > WIDTH:
    red_velocity[0] = -1 * red_velocity[0]
    if mode == False:
        if red_right == True:
            red = pygame.image.load(RED_LEFT).convert()
            red_right = False
        else:
            red = pygame.image.load(RED_RIGHT).convert()
            red_right = True

if red_boundary.top < 0 or red_boundary.bottom > HEIGHT:
    SOUND.play()
    red_velocity[1] = -1 * red_velocity[1]

if mode == True:
    if pacman_boundary.colliderect(red_boundary):
        red_velocity[0] = randint(-1,1)
        red_velocity[1] = randint(-1,1)


#####################################################



pacman_boundary = pacman_boundary.move(pacman_velocity)
blue_boundary = blue_boundary.move(blue_velocity)
orange_boundary = orange_boundary.move(orange_velocity)
pink_boundary = pink_boundary.move(pink_velocity)
red_boundary = red_boundary.move(red_velocity)

frame.fill(BACKGROUND_COLOUR)
frame.blit(pacman, pacman_boundary)
frame.blit(blue, blue_boundary)
frame.blit(orange, orange_boundary)
frame.blit(pink, pink_boundary)
frame.blit(red, red_boundary)
pygame.display.flip()

pygame.quit()

Answer 1

blue_right, orange_right, pink_right,\
          red_right, blue, orange, pink, red

This line is clearly broken. At least the 'global' statement of the former line has no effect here. Likely you are missing the trailing '\' in the line with the global statement or the corresponding line needs its own global statement.

Answer 2

Think that the problem is in the following lines:

def mode_switch():
    global mode
    blue_right, orange_right, pink_right,\
          red_right, blue, orange, pink, red

You defined mode as a global, but not the rest of variables that looks to be global at your program, e.g you need to update them to be global too - since you are modifying them inside your mode_switch function