Python and Pygame - Trying to bounce rectangle up and down

Question

I've been coding a simple platform game, where the user controls a square and has to get to the other side of the window, without colliding with the other squares. I want the other 4 squares to bounce up and down so I wrote this code:

import pygame
import os
import sys

os.environ['SDL_VIDEO_CENTERED'] = "1"
pygame.init()

#Variables:
width = 600
height = width / 16 * 9

running = True

#Colors
PINK = (255, 79, 161)
BLACK = (0, 0, 0)
BLUE = (0, 0, 255)

clock = pygame.time.Clock()

#MainRectProperties
mainRectX = 0
mainRectY = height / 2 - 20
mainRectSpeed = 250

#RectOneProperties:
rectOneX = 150
rectOneY = 0

#RectTwoPropeties:
rectTwoX = 250
rectTwoY = height - 20

#RectThreeProperties:
rectThreeX = 350
rectThreeY = 0

#RectFourProperties:
rectFourX = 450
rectFourY = height - 20

#Window:
window = pygame.display.set_mode((width, height))
windowText = pygame.display.set_caption("Pixel Animation")

#Rectangles:
mainRect = pygame.draw.rect(window, PINK, (mainRectX, mainRectY, 20, 20), 0)
obstacleRect1 = pygame.draw.rect(window, BLUE, (rectOneX, rectOneY, 20, 20), 0)
obstacleRect2 = pygame.draw.rect(window, BLUE, (rectTwoX, rectTwoY, 20, 20,), 0)
obstacleRect3 = pygame.draw.rect(window, BLUE, (rectThreeX, rectThreeY, 20, 20), 0)
obstacleRect4 = pygame.draw.rect(window, BLUE, (rectFourX, rectFourY, 20, 20), 0)
pygame.display.flip()

#UpdateMainRectFunction
def updateMainRect(x, y):
    window.fill(BLACK)
    mainRect = pygame.draw.rect(window, PINK, (mainRectX, mainRectY, 20, 20), 0)
    pygame.display.flip()
    clock.tick(250)

#GameLoop
while running:
    goingDown = True
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()

    if rectOneY < height - 21 and goingDown:
        print "b"
        pygame.draw.rect(window, BLACK, (rectOneX, rectOneY, 20, 20), 0)
        rectOneY += 1
        obstacleRect1 = pygame.draw.rect(window, BLUE, (rectOneX, rectOneY, 20, 20), 0)
        pygame.display.flip()
        clock.tick(100)
        if rectOneY == height - 21:
            goingDown = False
        else:
            goingDown = True

    if not goingDown and rectOneY != 0:
        print "a"
        pygame.draw.rect(window, BLACK, (rectOneX, rectOneY, 20, 20), 0)
        rectOneY -= 1
        obstacleRect1 = pygame.draw.rect(window, BLUE, (rectOneX, rectOneY, 20, 20), 0)
        pygame.display.flip()
        clock.tick(100)
        goingDown = False
        print rectOneY < height - 21 and goingDown     


    keys = pygame.key.get_pressed()
    #MovingRectCommands
    if keys[pygame.K_UP]:
        mainRectY -= 1
        updateMainRect(mainRectX, mainRectY)

    if keys[pygame.K_DOWN]:
        mainRectY += 1
        updateMainRect(mainRectX, mainRectY)

    if keys[pygame.K_LEFT]:
        mainRectX -= 1
        updateMainRect(mainRectX, mainRectY)

    if keys[pygame.K_RIGHT]:
        mainRectX += 1
        updateMainRect(mainRectX, mainRectY)

Basically the rectangle starts at the top of the screen and then sucessfuly hits the bottom of it. It prints a lot of "b's" to the console, as expected. Then, the rectangle moves up one pixel, the program prints one "a" to the console, but then it goes down again, even though the "if not going down and rectOneY != 0" expression is equal to True and the "if rectOneY < height - 21 and goingDown" expression is equal to False.

I've been trying to fix this for an hour at least, and I simply can't understand what's wrong and I could use some help.

I'd like you to point out what's the problem with my code(only the specific one I'm asking, not the millions of examples of bad code before it xD).

Thanks in advance.

Answer 1

The first line of your while running loop is goingDown = True. This sets the variable goingDown to true at the start of every iteration of the loop. You need to put the line goingDown = True before the loop.

It should look like this:

#GameLoop
goingDown = True
while running:
    ...