for语句不适用于pygame

Question

I've wanted to do some work with evolution simulation. The first part was to make independently moving squares on pygame. This seems to work except one slight hitch! When using the for statement line 43 it doesn't seem to apply it to all the squares that are generated only the first one. So one square moves as intended the rest just sit there doing nothing.. please help :D

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

pygame.init()

# set up the window
DISPLAYSURF = pygame.display.set_mode((500, 500), 0, 32)
pygame.display.set_caption('Drawing')

# set up the colors
BLACK = (  0,   0,   0)
WHITE = (255, 255, 255)
RED   = (255,   0,   0)
GREEN = (  0, 255,   0)
BLUE  = (  0,   0, 255)

# draw on the surface object
DISPLAYSURF.fill(BLACK)
robot_list=[]
counter =0
while counter < 26:
    x=random.randrange(1,500)
    x2 = x +6
    y= random.randrange(1,500)
    y2 = y +6
    robot_file=pygame.draw.polygon(DISPLAYSURF, WHITE, ((x, y), (x2, y), (x2, y2), (x, y2)))

    robot_list.append(robot_file)
    counter +=1

# run the game loop
while True:
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()
    for r in robot_list:
        time.sleep(0.1)
        pygame.draw.polygon(DISPLAYSURF, BLACK, ((x, y), (x2, y), (x2, y2), (x, y2)))
        rand2=random.randrange(1,6)
        rand1=random.randrange(-6,6)
        x += rand1
        x2+= rand1
        y+=rand2
        y2+=rand2

        pygame.draw.polygon(DISPLAYSURF, WHITE, ((x, y), (x2, y), (x2, y2), (x, y2)))
        pygame.display.update()

    pygame.display.update()

Answer 1

Simple: You only have one polygon in your code. I'm not sure what pygame.draw.polygon() returns; according to the documentation , it doesn't return anything useful.

What you need to do instead is put the coordinates of the polygon into the list robot_file (which is a pretty bad name for a list, BTW) and then update those coordinates.

Answer 2

it doesn't seem to apply it to all the squares that are generated only the first one.

The problem here is that you don't have any kind of square . You just draw something using the drawing function. To understand this better, maybe just create a class abstracting your game objects from the main loop.

Example:

class Polygon(object):
    def __init__(self):
       self.x = random.randrange(1,500)
       self.x2 = self.x + 6
       self.y = random.randrange(1,500)
       self.y2 = self.y + 6

    def move(self):
        rand2 = random.randrange(1,6)
        rand1 = random.randrange(-6,6)
        self.x += rand1
        self.x2 += rand1
        self.y += rand2
        self.y2 += rand2

    def draw(self, surface):
        pygame.draw.polygon(surface, WHITE, ((self.x, self.y), (self.x2, self.y), (self.x2, self.y2), (self.x, self.y2)))

for _ in xrange(26):
    robot_list.append(Polygon())

# run the game loop
while True:
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()
    for r in robot_list:
        r.move()
        r.draw(DISPLAYSURF)

    time.sleep(0.1)
    pygame.display.update()