Moving objects in PYGAME

Question

I have the code to move 2 objects across my screen. What I want them to do is reach the other side, and restart back at the beginning, however they just cross the screen and disappear.

import pygame, sys, time, random
from pygame.locals import *
pygame.init()
winW = 500
winH = 300
surface = pygame.display.set_mode ((winW, winH),0,32)

class Enemy():
    def __init__(self, char, xMoveAmnt, startY=0, startX=0):
        self.char = char
        self.x = startX
        self.y = startY
        self.startX=startX
        self.startY=startY
        self.xMoveAmnt = xMoveAmnt
        self.image = pygame.image.load(self.char)
        self.rect = self.image.get_rect()


    def moveChar(self):
        self.x += self.xMoveAmnt
        if self.rect.right >= 500:
            self.x=self.startX

enemyList = []
for i in range (0, 2):

    leftOrRight1 = random.randint(0,1)
    if leftOrRight1 == 0:
         leftOrRight = 0
         xMoveAmnt = 20
    elif leftOrRight1 == 1:
        leftOrRight = 500
        xMoveAmnt = -20
    enemyList.append(Enemy(("orc.png"), xMoveAmnt, random.randint(0, 300), leftOrRight))

while True:
    surface.fill ((255,255,255))
    for enemy in enemyList:
        enemy.moveChar()
        surface.blit(enemy.image, (enemy.x, enemy.y))
        time.sleep(00.04)        
    pygame.display.update()

What could be causing this?

What determines the position of an Enemy? Is it x: self.x +=... or is it rect: if self.rect.right >=... — Patashu
– Patashu, Commented Jun 18, 2013 at 23:38
self.x is the x of the object. Increasing it moves the object, the if is meant to move the object back to the starting position when it reaches the far side. — Stephen Sparks
– Stephen Sparks, Commented Jun 18, 2013 at 23:44

Patashu · Accepted Answer · 2013-06-18 23:45:37Z

1

    self.x += self.xMoveAmnt

Here, you increase the x of the Enemy to move it.

    if self.rect.right >= 500:

You were increasing x but now you are checking rect.right. If you are increasing x rect.right will not increase. Maybe you meant to do this:

    if self.x + self.rect.right >= 500:

?

answered Jun 18, 2013 at 23:45

Patashu

21.8k4 gold badges49 silver badges53 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

ninMonkey Over a year ago

rect.right is a property, it's equivalent to rect.x + rect.width

halflings · Accepted Answer · 2013-06-18 23:45:30Z

0

The problem here is that your doing a test on the position of the image's bounding rectangle ( if self.rect.right >= 500) while this rectangle is not updated (as you use a 'custom' variable, x, for the image's position).

Try doing something like that:

def moveChar(self):
    self.x += self.xMoveAmnt
    if self.x >= 500:
        self.x = self.startX

You could also use the modulo operator for that kind of things:

def moveChar(self):
    self.x = (self.x + self.xMoveAmnt) % 500

answered Jun 18, 2013 at 23:45

halflings

1,5461 gold badge14 silver badges36 bronze badges

Collectives™ on Stack Overflow

Moving objects in PYGAME

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related