Pygame change level - level made of list

Question

Hello i am new in pygame. And i have used this example: http://pygame.org/project/1061/ The example shows how to chack for collision, make a level from a list and movement. A great beginner example. I have modified it so it should be able to change level. I have tried deleting the rects once drawn but i can't figure that out. I have the problem that i can't change the level in my code:

import os
import random
import pygame

# Class for the orange dude
    class Player(object):

    def __init__(self, pos):
        players.append(self)
        self.rect = pygame.Rect(pos[0], pos[1], 16, 16)

    def move(self, dx, dy):

        # Move each axis separately. Note that this checks for collisions both times.
        if dx != 0:
            self.move_single_axis(dx, 0)
        if dy != 0:
            self.move_single_axis(0, dy)

    def move_single_axis(self, dx, dy):

    # Move the rect
        self.rect.x += dx
        self.rect.y += dy

    # If you collide with a wall, move out based on velocity
        for wall in walls:
            if self.rect.colliderect(wall.rect):
                if dx > 0: # Moving right; Hit the left side of the wall
                    self.rect.right = wall.rect.left
                if dx < 0: # Moving left; Hit the right side of the wall
                    self.rect.left = wall.rect.right
                if dy > 0: # Moving down; Hit the top side of the wall
                    self.rect.bottom = wall.rect.top
                if dy < 0: # Moving up; Hit the bottom side of the wall
                    self.rect.top = wall.rect.bottom

# Nice class to hold a wall rect
class Wall(object):

    def __init__(self, pos):
        walls.append(self)
        self.rect = pygame.Rect(pos[0], pos[1], 16, 16)

class Finish(object):

    def __init__(self, pos):
        finishes.append(self)
        self.rect = pygame.Rect(pos[0], pos[1], 16, 16)

# Variables
currentLevel = 1

# Initialise pygame
pygame.init()

# Set up the display
pygame.display.set_caption("Change level")
screen = pygame.display.set_mode((320, 240))

clock = pygame.time.Clock()
walls = [] # List to hold the walls
players = []
finishes = []

# Holds the level layout in a list of strings.
if currentLevel == 1:

    level = [
    "WWWWWWWWWWWWWWWWWWWW",
    "W                  W",
    "W  P      WWWWWW   W",
    "W   WWWW       W   W",
    "W   W        WWWW  W",
    "W WWW  WWWW        W",
    "W   W     W W      W",
    "W   W     W   WWW WW",
    "W   WWW WWW   W W  W",
    "W     W   W   W W  W",
    "WWW   W   WWWWW W  W",
    "W W      WW        W",
    "W W   WWWW   WWW   W",
    "W     W   F    W   W",
    "WWWWWWWWWWWWWWWWWWWW",
    ]
    # Parse the level string above
    x = y = 0
    for row in level:
        for col in row:
            if col == "W":
                Wall((x, y))
            if col == "P":
                Player((x, y))
            if col == "F":
                Finish((x, y))
            x += 16
        y += 16
        x = 0
if currentLevel == 2:

    level = [
    "WWWWWWWWWWWWWWWWWWWW",
    "W                  W",
    "W                  W",
    "W   WWWWWWWWWWWWW  W",
    "W                  W",
    "W         P        W",
    "W                  W",
    "W   WWWWWWWWWWWWW  W",
    "W                  W",
    "W   WWWWWWWWWWWWW  W",
    "W                  W",
    "W         F        W",
    "W                  W",
    "W                  W",
    "WWWWWWWWWWWWWWWWWWWW",
    ]

    # Parse the level string above
    x = y = 0
    for row in level:
        for col in row:
            if col == "W":
                Wall((x, y))
            if col == "P":
                Player((x, y))
            if col == "F":
                Finish((x, y))
            x += 16
        y += 16
        x = 0

running = True
while running:

    clock.tick(60)

    for e in pygame.event.get():
        if e.type == pygame.QUIT:
            running = False
        if e.type == pygame.KEYDOWN and e.key == pygame.K_ESCAPE:
            running = False

    # Move the player if an arrow key is pressed
    key = pygame.key.get_pressed()
    if key[pygame.K_LEFT]:
        player.move(-2, 0)
    if key[pygame.K_RIGHT]:
        player.move(2, 0)
    if key[pygame.K_UP]:
        player.move(0, -2)
    if key[pygame.K_DOWN]:
        player.move(0, 2)

    # Just added this to make it slightly fun ;)
    for player in players:
        for finish in finishes:
            if player.rect.colliderect(finish.rect): 
                currentLevel = 2 # Doesn't work

    # Draw the scene
    screen.fill((0, 0, 0))
    for wall in walls:
        pygame.draw.rect(screen, (255, 255, 255), wall.rect)
    for player in players:
        pygame.draw.rect(screen, (255, 200, 0), player.rect)
    for finish in finishes:
        pygame.draw.rect(screen, (0, 200, 0), finish.rect)
    pygame.display.flip() 

Answer 1

You just change the currentLevel variable, but you never actually change the walls, players and finishes lists (only the code inside the while loop is executed at this time).

A very simple way to solve this issue is to put the code that "loads" the level into a function and call it when the player reaches the end of the level, e.g.:

import os
import random
import pygame

# Class for the orange dude
class Player(object):

    def __init__(self, pos):
        self.rect = pygame.Rect(pos[0], pos[1], 16, 16)

    def move(self, dx, dy):

        # Move each axis separately. Note that this checks for collisions both times.
        if dx != 0:
            self.move_single_axis(dx, 0)
        if dy != 0:
            self.move_single_axis(0, dy)

    def move_single_axis(self, dx, dy):

    # Move the rect
        self.rect.x += dx
        self.rect.y += dy

    # If you collide with a wall, move out based on velocity
        for wall in walls:
            if self.rect.colliderect(wall.rect):
                if dx > 0: # Moving right; Hit the left side of the wall
                    self.rect.right = wall.rect.left
                if dx < 0: # Moving left; Hit the right side of the wall
                    self.rect.left = wall.rect.right
                if dy > 0: # Moving down; Hit the top side of the wall
                    self.rect.bottom = wall.rect.top
                if dy < 0: # Moving up; Hit the bottom side of the wall
                    self.rect.top = wall.rect.bottom

# Nice class to hold a wall rect
class Wall(object):

    def __init__(self, pos):
        self.rect = pygame.Rect(pos[0], pos[1], 16, 16)

class Finish(object):

    def __init__(self, pos):
        self.rect = pygame.Rect(pos[0], pos[1], 16, 16)

# Variables
currentLevel = 0

# Initialise pygame
pygame.init()

# Set up the display
pygame.display.set_caption("Change level")
screen = pygame.display.set_mode((320, 240))

clock = pygame.time.Clock()

levels = [[
    "WWWWWWWWWWWWWWWWWWWW",
    "W                  W",
    "W  P      WWWWWW   W",
    "W   WWWW       W   W",
    "W   W        WWWW  W",
    "W WWW  WWWW        W",
    "W   W     W W      W",
    "W   W     W   WWW WW",
    "W   WWW WWW   W W  W",
    "W     W   W   W W  W",
    "WWW   W   WWWWW W  W",
    "W W      WW        W",
    "W W   WWWW   WWW   W",
    "W     W   F    W   W",
    "WWWWWWWWWWWWWWWWWWWW",
    ],
    [
    "WWWWWWWWWWWWWWWWWWWW",
    "W                  W",
    "W                  W",
    "W   WWWWWWWWWWWWW  W",
    "W                  W",
    "W         P        W",
    "W                  W",
    "W   WWWWWWWWWWWWW  W",
    "W                  W",
    "W   WWWWWWWWWWWWW  W",
    "W                  W",
    "W         F        W",
    "W                  W",
    "W                  W",
    "WWWWWWWWWWWWWWWWWWWW",
    ]]

def load_level(level):
    walls = []
    players = []
    finishes = []

    # Parse the level string above
    x = y = 0
    for row in levels[level]:
        for col in row:
            if col == "W":
                walls.append(Wall((x, y)))
            if col == "P":
                players.append(Player((x, y)))
            if col == "F":
                finishes.append(Finish((x, y)))
            x += 16
        y += 16
        x = 0
    return walls, players, finishes

walls, players, finishes = load_level(currentLevel)
running = True
while running:

    clock.tick(60)

    for e in pygame.event.get():
        if e.type == pygame.QUIT:
            running = False
        if e.type == pygame.KEYDOWN and e.key == pygame.K_ESCAPE:
            running = False

    # Move the player if an arrow key is pressed
    key = pygame.key.get_pressed()
    if key[pygame.K_LEFT]:
        player.move(-2, 0)
    if key[pygame.K_RIGHT]:
        player.move(2, 0)
    if key[pygame.K_UP]:
        player.move(0, -2)
    if key[pygame.K_DOWN]:
        player.move(0, 2)

    # Just added this to make it slightly fun ;)
    for player in players:
        for finish in finishes:
            if player.rect.colliderect(finish.rect): 
                currentLevel += 1
                walls, players, finishes = load_level(currentLevel)

    # Draw the scene
    screen.fill((0, 0, 0))
    for wall in walls:
        pygame.draw.rect(screen, (255, 255, 255), wall.rect)
    for player in players:
        pygame.draw.rect(screen, (255, 200, 0), player.rect)
    for finish in finishes:
        pygame.draw.rect(screen, (0, 200, 0), finish.rect)
    pygame.display.flip()