python - How to avoid a flickering game display? -

for reason weird squiggly wave keeps coming on minecraft game. cannot calculate problem need because have worked hard come game scratch. if see problems cause strange wave please respond possible.

here's code:

import pygame, sys, random pygame.locals import *  black = (0, 0, 0      ) brown = (153, 76, 0   ) green = (0, 255, 0    ) blue  = (0, 0, 255    ) white = (255, 255, 255)  dirt  = 0 grass = 1 water = 2 coal  = 3  textures = {                 dirt  : pygame.image.load("dirt.png"),                 grass : pygame.image.load("grass.png"),                 water : pygame.image.load("water.png"),                 coal  : pygame.image.load("coal.png")         }  inventory = {                dirt  : 0,                grass : 0,                water : 0,                coal  : 0         }  tilesize  = 20 mapwidth  = 30 mapheight = 20  player = pygame.image.load("player.png") playerpos = [0, 0]  resources = [dirt,grass,water,coal] tilemap = [ [dirt w in range(mapwidth)] h in range(mapheight) ]  pygame.init() displaysurf = pygame.display.set_mode((mapwidth*tilesize, mapheight*tilesize + 50))  invfont = pygame.font.font(none, 18)  rw in range(mapheight):     cl in range(mapwidth):         randomnumber = random.randint(0, 15)         if randomnumber == 0:             tile = coal         elif randomnumber == 1 or randomnumber == 2:             tile = water         elif randomnumber >3 , randomnumber <= 7:             tile = grass         else:             tile = dirt         tilemap[rw][cl] = tile  while true:     event in pygame.event.get():         if event.type == quit:             pygame.quit()             sys.exit()         elif event.type == keydown:             if event.key == k_right , playerpos[0] < mapwidth - 1:                 playerpos[0] += 1             if event.key == k_left , playerpos[0] > 0:                 playerpos[0] -= 1             if event.key == k_up , playerpos[1] > 0:                 playerpos[1] -= 1             if event.key == k_down , playerpos[1] < mapheight -1:                 playerpos[1] += 1             if event.key == k_space:                 currenttile = tilemap[playerpos[1]][playerpos[0]]                 inventory[currenttile] += 1                 tilemap[playerpos[1]][playerpos[0]] = dirt             if (event.key == k_1):                 currenttile = tilemap[playerpos[1]][playerpos[0]]                 if inventory[dirt] > 0:                     inventory[dirt] -= 1                     tilemap[playerpos[1]][playerpos[0]] = dirt                     inventory[currenttile] += 1      row in range(mapheight):         column in range(mapwidth):             displaysurf.blit(textures[tilemap[row][column]], (column*tilesize,row*tilesize))          displaysurf.blit(player,(playerpos[0]*tilesize,playerpos[1]*tilesize))          placeposition = 10         item in resources:             displaysurf.blit(textures[item],(placeposition,mapheight*tilesize+20))             placeposition += 30             textobj = invfont.render(str(inventory[item]), true, white, black)             displaysurf.blit(textobj,(placeposition,mapheight*tilesize+20))             placeposition += 50          pygame.display.update() 

the problem you call pygames pygame.display.update() function each iteration in mapheight loop. try call pygame.display.update() or pygame.display.flip() afterwards:

#import , game set ...  #main game loop while true:     #event loop     event in pygame.event.get():         if event.type == quit:             pygame.quit()             sys.exit()     ...      row in range(mapheight):         column in range(mapwidth):             displaysurf.blit(textures[tilemap[row][column]], (column*tilesize,row*tilesize))          displaysurf.blit(player,(playerpos[0]*tilesize,playerpos[1]*tilesize))          placeposition = 10         item in resources:             displaysurf.blit(textures[item],(placeposition,mapheight*tilesize+20))             placeposition += 30             textobj = invfont.render(str(inventory[item]), true, white, black)             displaysurf.blit(textobj,(placeposition,mapheight*tilesize+20))             placeposition += 50      #update (draw) screen     pygame.display.update() 

hope helps :)