python - How to make a sprite correct path? -

i trying create small , simple simulation makes meteor appear in middle of screen , move away... until users presses key. while key pressed, path corrected dynamically new path.

i tried 2 different method, first keydown, , pygame.key.get_pressed() function, in both cases, after release key, image "meteor" drops down again orginal path.

i hoping 1 indicate me doing wrong.

here code far:

import pygame,sys pygame.locals import * colors import * import random   fps = 30  fpsclock = pygame.time.clock()   pygame.init()  x_display = 400 y_display = 400  displaysurf = pygame.display.set_mode((x_display, y_display)) displaysurf.fill(silver) pygame.display.set_caption("meteor")  x_real_max = x_display/2 y_real_max = y_display/2 x_center = 0 y_center = 0  xmeteor = 40 ymeteor = 20 xcentermeteor = 0 ycentermeteor = 0 xposmeteor = xcentermeteor + (200 - (xmeteor/2)) yposmeteor = ycentermeteor + (200 - (ymeteor/2))  imgmeteor = pygame.image.load("desktop\imgmeteor.png")  viseffect = 1.05   while true:      xmeteor *= viseffect     ymeteor *= viseffect      xcentermeteor *= viseffect     ycentermeteor *= viseffect      xposmeteor = xcentermeteor + (200 - (xmeteor/2))     yposmeteor = ycentermeteor + (200 - (ymeteor/2))      #pressed  = pygame.key.get_pressed()     #if pressed[pygame.k_w]:         #yposmeteor -= 10      if xmeteor > 150:         xmeteor = 40         ymeteor = 20         xcentermeteor = random.randrange(-100, 100)         ycentermeteor = random.randrange(-100, 100)         xposmeteor = xcentermeteor + (200 - (xmeteor/2))         yposmeteor = ycentermeteor + (200 - (ymeteor/2))      meteor = pygame.transform.scale(imgmeteor, (int(xmeteor),int(ymeteor)))       event in pygame.event.get():         if event.type == quit:             pygame.quit()             sys.exit()         #if event.type == keydown:             #if event.key == k_w:                 #yposmeteor -= 50         #elif event.type == keyup:             #yposmeteor = yposmeteor       displaysurf.blit(meteor, (xposmeteor, yposmeteor))     pygame.display.update()     fpsclock.tick(fps)     displaysurf.fill(silver) 

you're updating wrong variable. yposmeteor clobbered every time through loop, when change variable there no lasting effect. want change either ycentermeteor or ymeteor.