[PyGame] Space Invaders Python Bug?

[CJMinecraft]

So recently I have been working on a project. I was trying to recreate Space Invaders using pygame. I am using Python 3.1.4 and I feel like I found a python bug. When the game resets, the aliens fail to move down and they continue to bounce off the side of the window.

import random
import pygame
from pygame.locals import *

WIDTH = 600
HEIGHT = 600
MOVEMENT_AMOUNT = (WIDTH / 600) * (HEIGHT / 600) * 0.25
ALIEN_WIDTH = 50
ALIEN_HEIGHT = 38
ALIENS_PER_ROW = int((WIDTH / 600) * 10)
NUMBER_OF_ROWS = int((HEIGHT / 600) * 3)

pygame.init()

class Entity(object):

    def __init__(self, width, height, imagePath):
        self.width = width
        self.height = height
        self.x = 0
        self.y = 0
        self.image = pygame.image.load(imagePath).convert_alpha()
        self.image.fill((255, 255, 255, 128), None, pygame.BLEND_RGBA_MULT)
        self.image = pygame.transform.scale(self.image, (self.width, self.height))

    def getWidth(self):
        return self.width

    def getHeight(self):
        return self.height

    def getX(self):
        return self.x

    def getY(self):
        return self.y

    def setX(self, x):
        self.x = x

    def setY(self, y):
        self.y = y

    def draw(self, screen):
        screen.blit(self.image, Rect(self.x, self.y, self.width, self.height))

    def drawColour(self, screen, newColour):
        self.image.fill(newColour[0:3] + (0,), None, pygame.BLEND_RGBA_ADD)
        screen.blit(self.image, Rect(self.x, self.y, self.width, self.height))

    def increaseX(self, amount):
        if self.x <= WIDTH - self.width and self.x >= 0:
            self.x = self.x + amount
        elif self.x < 0:
            self.x = 1
        else:
            self.x = WIDTH - self.width - 1

    def increaseY(self, amount):
        if self.y <= HEIGHT - self.height and self.y >= 0:
            self.y = self.y + amount
        elif self.y < 0:
            self.y = 1
        else:
            self.y = HEIGHT - self.height - 1

class Bullet(Entity):

    def __init__(self, width, height, imagePath):
        self.width = width
        self.height = height
        self.x = 0
        self.y = 0
        self.image = pygame.image.load(imagePath).convert_alpha()
        self.image.fill((255, 255, 255, 128), None, pygame.BLEND_RGBA_MULT)
        self.image = pygame.transform.scale(self.image, (self.width, self.height))
        self.moving = False

    def isMoving(self):
        return self.moving

    def setMoving(self, moving):
        self.moving = moving

screen = pygame.display.set_mode((WIDTH,HEIGHT), pygame.HWSURFACE)
pygame.display.set_caption("Space Invaders")

cannon = Entity(80, 48, "cannon.png")
cannon.setX(int(WIDTH / 2) - int(cannon.width / 2))
cannon.setY(HEIGHT - cannon.getHeight())

bullets = []
aliens = []

aliensLeft = False
aliensDown = False
restart = False

bulletFireCooldown = 0
bulletFireCooldownUse = False

moveDownBool = False
moveLeftBool = False
dontMoveBool = False
lastY = 0

class Alien(Entity):

    def __init__(self, width, height, imagePath):
        self.width = width
        self.height = height
        self.x = 0
        self.y = 0
        self.image = pygame.image.load(imagePath).convert_alpha()
        self.image.fill((255, 255, 255, 128), None, pygame.BLEND_RGBA_MULT)
        self.image = pygame.transform.scale(self.image, (self.width, self.height))
        self.lastY = 0

def createAliens():
    for y in range(0, NUMBER_OF_ROWS):
        for x in range(0, ALIENS_PER_ROW):
            alien = Alien(ALIEN_WIDTH, ALIEN_HEIGHT, "alien.png")
            alien.setY(y * ALIEN_HEIGHT)
            alien.setX(x * ALIEN_WIDTH)
            aliens.append(alien)

def resetGame():
    global restart
    global moveLeftBool
    global dontMoveBool
    global moveDownBool
    global lastY
    restart = False
    aliens[:] = []
    createAliens()
    cannon.setX(int(WIDTH / 2) - int(cannon.width / 2))
    cannon.setY(HEIGHT - cannon.getHeight())
    moveLeftBool = False
    lastY = aliens[0].y
    moveDownBool = False
    dontMoveBool = False

def moveAliens():
    global moveLeftBool
    global dontMoveBool
    global moveDownBool
    global lastY
    for alien in aliens:
        if moveLeftBool:
            if not dontMoveBool:
                alien.increaseX(-MOVEMENT_AMOUNT / int((HEIGHT / 600) * 2) / 2)
                if alien.x <= 1:
                    moveLeftBool = False
                    moveDownBool = True
                    dontMoveBool = True
                    lastY = aliens[0].y
        else:
            if not dontMoveBool:
                alien.increaseX(MOVEMENT_AMOUNT / int((HEIGHT / 600) * 2) / 2)
                if alien.x >= WIDTH - ALIEN_WIDTH:
                    moveLeftBool = True
                    moveDownBool = True
                    dontMoveBool = True
                    lastY = aliens[0].y
        if moveDownBool:
            alien.increaseY(MOVEMENT_AMOUNT / int((HEIGHT / 600) * 2))
            if alien.y == lastY + ALIEN_HEIGHT:
                moveDownBool = False
                dontMoveBool = False
                print("Moved down", lastY)
        if alien.y >= HEIGHT - alien.height - cannon.height:
            resetGame()

#alienColours = ((0, 255, 255),( 0,  0, 255),(255,0,255),(128, 128, 128),(0,128,0),(0, 255,0),(128,0,0),(0, 0,128),(128, 128,0),(128,  0, 128),(255,0,0),(192, 192, 192),(0, 128, 128),(255, 255, 255),(255, 255,0))

createAliens()

while True:
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            break

    if event.type == KEYDOWN:
        if event.key == K_RIGHT:
            cannon.increaseX(MOVEMENT_AMOUNT)
        if event.key == K_LEFT:
            cannon.increaseX(-MOVEMENT_AMOUNT)
        if event.key == K_SPACE and bulletFireCooldown == 0:
            bulletFireCooldownUse = True
            bullet = Bullet(10, 20, "bullet.png")
            bullet.setX(cannon.getX() + (cannon.getWidth() / 2) - (bullet.getWidth() / 2))
            bullet.setY(HEIGHT - cannon.getHeight() - bullet.getHeight())
            bullet.setMoving(True)
            bullets.append(bullet)
        if event.key == K_t:
            MOVEMENT_AMOUNT = (WIDTH / 600) * (HEIGHT / 600) * 1
        else:
            MOVEMENT_AMOUNT = (WIDTH / 600) * (HEIGHT / 600) * 0.25

    for bullet in bullets:
        bullet.setY(bullet.getY() - MOVEMENT_AMOUNT)
        bullet.draw(screen)
        if bullet.getY() == 0 - bullet.getHeight():
            bullet.setMoving(False)
            bullets.remove(bullet)

    if bulletFireCooldownUse:
        bulletFireCooldown = bulletFireCooldown + 1
        if bulletFireCooldown == int((HEIGHT / 600) * 300):
            bulletFireCooldownUse = False
            bulletFireCooldown = 0

    for alien in aliens:
        for bullet in bullets:
            if bullet.getX() >= alien.getX() and bullet.getX() + bullet.getWidth() <= alien.getX() + alien.getWidth():
                if bullet.getY() >= alien.getY() and bullet.getY() + bullet.getHeight() <= alien.getY() + alien.getHeight():
                    bullets.remove(bullet)
                    aliens.remove(alien)
        alien.draw(screen)
    moveAliens()

    if len(aliens) == 0:
        restart = True
    if restart:
        restart = False
        resetGame()
        
    cannon.draw(screen)
    pygame.display.flip()
    pygame.display.update()
    screen.fill(Color("black"))

pygame.exit()

I have been tracking the output of the lastY variable and the alien.y variable. 
Alien.y:
Moved down 38.0
Moved down 75.875
Moved down 113.75
Moved down 151.5
Moved down 189.25
Moved down 226.875
Moved down 264.5
Moved down 302.0
Moved down 339.5
Moved down 376.875
Moved down 414.25
Moved down 38.0
Moved down 76.0
Moved down 76.0
Moved down 76.125

Last Y:
Moved down 38.0
Moved down 75.875
Moved down 113.75
Moved down 151.5
Moved down 189.25
Moved down 226.875
Moved down 264.5
Moved down 302.0
Moved down 339.5
Moved down 376.875
Moved down 414.25
Moved down 38.0
Moved down 76.0
Moved down 76.0
Moved down 76.125
Moved down 76.125
Moved down 76.375
Moved down 76.5
Moved down 76.625
Moved down 76.625
Moved down 77.125

[metulburr]

1) First of all include your images so we can run your program without tinkering with your code.
2) 99999/100000 times when you call out a bug in the language, its really you created the bug in your code, not a language bug
3) Using global keywords is notorious for bugs to creep in your code
4) use classes more. You have classes but the majority of the meat is outside of them. 

5) Your over complicating the rect process

        screen.blit(self.image, Rect(self.x, self.y, self.width, self.height))

pygame.Rect has x,y,width, and height attributes, and more. You are just making things redundant by not using them properly. As well as introducing possible bugs into your program. All the getters and setters are not needed as as you are just recreating the wheel by not using Rects to their full potential. 

pygame.Rect also has collision detection to identify a collision with another pygame.Rect which you should be using, but are not. 

Here is our tutorial in which demonstrates how to use rects
https://python-forum.io/Thread-PyGame-Ba...ing-part-3

[georgecoopers]

Nicely Coded