I cant move my image in pygame with arrow keys

Question

Can someone show me why the up down arrow keys won't move my image? I'm using Python 3 and Pygame 1.91. No errors. Just disappointment. The pertinent section are lines 65-115 (Beginning of Display function to end of Move_Paddle function).

import pygame
import time
import sys
from pygame.locals import *


pygame.init()

display_width = 800
display_height = 600

black = (0, 0, 0)                   #Colors
white = (255, 255, 255)

pygame.display.set_caption('Pong')  #Title

clock = pygame.time.Clock()         #Clock

gameDisplay = pygame.display.set_mode((display_width,display_height))  #Defines "window" and width/height variables


BallImg = pygame.image.load('C:\Python\Programs\Pong\Ball.png')
Paddle_PlayerImg = pygame.image.load('C:\Python\Programs\Pong\Paddle.png')
Paddle_CompImg = pygame.image.load('C:\Python\Programs\Pong\Paddle1.png')


def Ball(BLx,BLy):

    gameDisplay.blit(BallImg,(BLx ,BLy ))

def Paddle_Player(PPx,PPy):

    gameDisplay.blit(Paddle_PlayerImg, (display_width * 0.725 ,display_height * .166 ))

def Paddle_Comp(PCx,PCy):

    gameDisplay.blit(Paddle_CompImg, (PCx,PCy))

    pygame.display.flip()


gameDisplay.fill(black)

BLx = display_width * 0.475
BLy = display_height * .75 

PPx = display_width * 0.725 
PPy = display_height * .166

PCx = display_width * 0.125
PCy = display_height * .166      

Ball(BLx,BLy)
Paddle_Player(PPx,PPy)
Paddle_Comp(PCx,PCy)

pygame.display.flip()

clock.tick(15)

def Display():
    gameDisplay.fill(black)

    BLx = display_width * 0.475
    BLy = display_height * .75 

    PPx = display_width * 0.725 
    PPy = display_height * .166

    PCx = display_width * 0.125
    PCy = display_height * .166      

    Ball(BLx,BLy)
    Paddle_Player(PPx,PPy)
    Paddle_Comp(PCx,PCy)

    pygame.display.update()



def Move_Paddle():    
    PPx = display_width * 0.725 
    PPy = display_height * .166
    PPy_change = 0
    gameExit = False

    while not gameExit:

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

            if event.type == KEYDOWN:
                if event.key == K_DOWN:
                    PPy_change = -5
                if event.key == K_UP:
                    PPy_change = 5

            if event.type == pygame.KEYUP:
                if event.key == K_UP or event.key == K_DOWN:
                    PPy_change = 0

        PPy += PPy_change
    pygame.display.update()
    Paddle_Player(PPx,PPy)

    clock.tick(60)               

Move_Paddle()
Display()

quit()

have you read [this SO QA](http://stackoverflow.com/questions/16044229/how-to-get-keyboard-input-in-pygame) and [this one](http://stackoverflow.com/questions/25494726/how-to-use-pygame-keydown)? I think they would be useful on a number of fronts — Pynchia, Aug 06 '15 at 16:08
I highly suggest doing a pygame tutorial rather than trying to feel your way through blindly. This will help you understand the *basics* of game-dev as well as the flow of game-dev using pygame. Check out the [pygame website](https://pygame.org/wiki/tutorials) for a list of tutorials. — Michael S Priz, Aug 06 '15 at 16:31

score 1 · Answer 1 · answered Aug 06 '15 at 16:01

1

I think the issue is that in your Move_Paddle() function , the code to update the display and move the player , I am guessing - Paddle_Player() function - is outside the while loop, so that code is only hit after you exit. You should move them inside the while loop. Example -

def Move_Paddle():    
    PPx = display_width * 0.725 
    PPy = display_height * .166
    PPy_change = 0
    gameExit = False

    while not gameExit:

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

            if event.type == KEYDOWN:
                if event.key == K_DOWN:
                    PPy_change = -5
                if event.key == K_UP:
                    PPy_change = 5

            if event.type == pygame.KEYUP:
                if event.key == K_UP or event.key == K_DOWN:
                    PPy_change = 0

        PPy += PPy_change
        pygame.display.update()
        Paddle_Player(PPx,PPy)

        clock.tick(60)

answered Aug 06 '15 at 16:01

Anand S Kumar

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Thanks. Still nothing though. If it helps, i printed K_DOWN and PPy_change and it spat out "-5" and "274" on separate lines while I held the button down. – Press_Any_Key Aug 06 '15 at 16:09
try moving the `Paddle_Player` function above the `display.update()` one. – Anand S Kumar Aug 06 '15 at 16:12
@ Anand, unfortunately that didn't do it either--I'll have to pour over the documentation. I appreciate your help. – Press_Any_Key Aug 06 '15 at 16:36
@Press_Any_Key is it still that nothing is moved? or did the behaviour change? – Anand S Kumar Aug 06 '15 at 16:41
Try making a small change like - in the if condition - `if event.key == K_DOWN:` - do - `PPy += PPy_change` (after setting PPy_change) , and check if that does anything. – Anand S Kumar Aug 06 '15 at 16:42
No change. Obviously the program knows i'm pressing the key, but the object isn't moving. – Press_Any_Key Aug 06 '15 at 16:44
No change with the latest changes I asked? – Anand S Kumar Aug 06 '15 at 16:47
Ok, see above where it says that with the print function i got -5 on one line and 274 on the next (continuously) now i'm getting 0 and 274 – Press_Any_Key Aug 06 '15 at 16:49
No, I am checking maybe the issue is that since you are resetting `PPy_change` to 0 on KEYUP event, maybe its happenning too fast, before the display could update. Try change the PPy during the KEYDOWN event directly – Anand S Kumar Aug 06 '15 at 16:53
I'm either getting no change or "referenced before assignment" – Press_Any_Key Aug 06 '15 at 17:23
What is the latest code ? Can you please update the question? – Anand S Kumar Aug 06 '15 at 17:25
why did you remove `PPy_change = -5` , let it be there before using it in `PPy += PPy_change` . – Anand S Kumar Aug 06 '15 at 17:29
Now I'm back to -5, 274. No movement. – Press_Any_Key Aug 06 '15 at 17:37

score 0 · Answer 2 · answered Aug 06 '15 at 17:27

import pygame
import time
import sys
from pygame.locals import *


pygame.init()

display_width = 800
display_height = 600

black = (0, 0, 0)                   #Colors
white = (255, 255, 255)

cellSize = 11

pygame.display.set_caption('Pong')  #Title

clock = pygame.time.Clock()         #Clock

gameDisplay = pygame.display.set_mode((display_width,display_height))  #Defines "window" and width/height variables


BallImg = pygame.image.load('C:\Python\Programs\Pong\Ball.png')
Paddle_PlayerImg = pygame.image.load('C:\Python\Programs\Pong\Paddle.png')
Paddle_CompImg = pygame.image.load('C:\Python\Programs\Pong\Paddle1.png')


def Ball(BLx,BLy):

    gameDisplay.blit(BallImg,(BLx ,BLy ))

def Paddle_Player(PPx,PPy):

    gameDisplay.blit(Paddle_PlayerImg, (display_width * 0.725 ,display_height * .166 ))

def Paddle_Comp(PCx,PCy):

    gameDisplay.blit(Paddle_CompImg, (PCx,PCy))

    pygame.display.flip()


gameDisplay.fill(black)

BLx = display_width * 0.475
BLy = display_height * .75 

PPx = display_width * 0.725 
PPy = display_height * .166

PCx = display_width * 0.125
PCy = display_height * .166



Ball(BLx,BLy)
Paddle_Player(PPx,PPy)
Paddle_Comp(PCx,PCy)

pygame.display.flip()

clock.tick(15)

def Display():
    gameDisplay.fill(black)

    BLx = display_width * 0.475
    BLy = display_height * .75 

    PPx = display_width * 0.725 
    PPy = display_height * .166

    PCx = display_width * 0.125
    PCy = display_height * .166      

    Ball(BLx,BLy)
    Paddle_Player(PPx,PPy)
    Paddle_Comp(PCx,PCy)

    pygame.display.update()



def Move_Paddle():    
    PPx = display_width * 0.725 
    PPy = display_height * .166
    PPy_change = 0
    gameExit = False

    while not gameExit:

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

            if event.type == KEYDOWN:
                if event.key == K_DOWN:
                    PPy += PPy_change
                    print(PPy_change)
                    print(K_DOWN)
                if event.key == K_UP:
                    PPy_change = 5

            if event.type == pygame.KEYUP:
                if event.key == K_UP or event.key == K_DOWN:
                    PPy_change = 0

        PPy += PPy_change
        Paddle_Player(PPx,PPy)
        pygame.display.update()


        clock.tick(60)               

Move_Paddle()
Display()

quit()

score 0 · Answer 3 · answered Aug 07 '15 at 16:08

I fixed It!!!!

# I changed this function:

def Paddle_Player(PPx,PPy):

gameDisplay.blit(Paddle_PlayerImg, (display_width * 0.725 ,display_height * .166 ))

#...to this! That's all there was to it.

        def Paddle_Player(PPx,PPy):

gameDisplay.blit(Paddle_PlayerImg, (PPx,PPy))

#The variables were already defined below!

I cant move my image in pygame with arrow keys

3 Answers3

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