My problem is hard to explain so please run the code to see what's going on
I'm trying to adapt the code of a snake game so that the snake cannot collide with the screen boundaries. I'm using existing code that can be found here code on stackexchange. I'm using the revised version by Gareth Rees (see the bottom part of his answer).
I added the no boundaries option (global boolean WORLD_BOUNDARIES = False) but I have problems to get it right basically because I'm not used to pythons syntax.
My adapted code looks like this. The changed/added code is between '''****...''' comments inside the snake class' update function). The code below can be safely executed but has some bugs related to the no boundaries. I did try to fix the bug in the down direction but it is not working so I commented it out.
from collections import deque
from itertools import *
import pygame
from random import randrange
import sys
from pygame.locals import *
class Vector(tuple):
"""A tuple that supports some vector operations.
>>> v, w = Vector((1, 2)), Vector((3, 4))
>>> v + w, w - v, v * 10, 100 * v, -v
((4, 6), (2, 2), (10, 20), (100, 200), (-1, -2))
"""
def __add__(self, other): return Vector(v + w for v, w in zip(self, other))
def __radd__(self, other): return Vector(w + v for v, w in zip(self, other))
def __sub__(self, other): return Vector(v - w for v, w in zip(self, other))
def __rsub__(self, other): return Vector(w - v for v, w in zip(self, other))
def __mul__(self, s): return Vector(v * s for v in self)
def __rmul__(self, s): return Vector(v * s for v in self)
def __neg__(self): return -1 * self
FPS = 60 # Game frames per second
SEGMENT_SCORE = 50 # Score per segment
SNAKE_SPEED_INITIAL = 4.0 # Initial snake speed (squares per second)
SNAKE_SPEED_INCREMENT = 0.25 # Snake speeds up this much each time it grows
SNAKE_START_LENGTH = 4 # Initial snake length in segments
WORLD_SIZE = Vector((20, 20)) # World size, in blocks
BLOCK_SIZE = 24 # Block size, in pixels
WORLD_BOUNDARIES = False
BACKGROUND_COLOR = 45, 45, 45
SNAKE_COLOR = 0, 255, 0
FOOD_COLOR = 255, 0, 0
DEATH_COLOR = 255, 0, 0
TEXT_COLOR = 255, 255, 255
DIRECTION_UP = Vector(( 0, -1))
DIRECTION_DOWN = Vector(( 0, 1))
DIRECTION_LEFT = Vector((-1, 0))
DIRECTION_RIGHT = Vector(( 1, 0))
DIRECTION_DR = DIRECTION_DOWN + DIRECTION_RIGHT
# Map from PyGame key event to the corresponding direction.
KEY_DIRECTION = {
K_w: DIRECTION_UP, K_UP: DIRECTION_UP,
K_s: DIRECTION_DOWN, K_DOWN: DIRECTION_DOWN,
K_a: DIRECTION_LEFT, K_LEFT: DIRECTION_LEFT,
K_d: DIRECTION_RIGHT, K_RIGHT: DIRECTION_RIGHT,
}
class Snake(object):
def __init__(self, start, start_length):
self.speed = SNAKE_SPEED_INITIAL # Speed in squares per second.
self.timer = 1.0 / self.speed # Time remaining to next movement.
self.growth_pending = 0 # Number of segments still to grow.
self.direction = DIRECTION_UP # Current movement direction.
self.segments = deque([start - self.direction * i
for i in xrange(start_length)])
def __iter__(self):
return iter(self.segments)
def __len__(self):
return len(self.segments)
def change_direction(self, direction):
"""Update the direction of the snake."""
# Moving in the opposite direction of current movement is not allowed.
if self.direction != -direction:
self.direction = direction
def head(self):
"""Return the position of the snake's head."""
return self.segments[0]
def tail(self):
"""Return the tail of the snake."""
return deque(islice(self.segments, 1, None))
def update(self, dt, direction):
"""Update the snake by dt seconds and possibly set direction."""
self.timer -= dt
if self.timer > 0:
# Nothing to do yet.
return
# Moving in the opposite direction of current movement is not allowed.
if self.direction != -direction:
self.direction = direction
self.timer += 1 / self.speed
'''************************************************************************************
***************************************************************************************
***************************************************************************************'''
if not WORLD_BOUNDARIES:
head = self.head()
if self.direction == DIRECTION_DOWN and head[1] == WORLD_SIZE[1]-1:
self.segments[0]=Vector((head[0], 0))
# new_head = (head[0], 0)
# new_tail = deque([x+self.direction for x in self.tail()])
# self.segments = new_tail.extendleft([new_head])
# print new_head
# print new_tail
if self.direction == DIRECTION_UP and head[1] == 0:
self.segments[0]=Vector((head[0], WORLD_SIZE[1]-1))
if self.direction == DIRECTION_RIGHT and head[0] == WORLD_SIZE[0]-1:
self.segments[0]=Vector((0, head[1]))
if self.direction == DIRECTION_LEFT and head[0] == 0:
self.segments[0]=Vector((WORLD_SIZE[0]-1, head[1]))
'''************************************************************************************
***************************************************************************************
***************************************************************************************'''
# Add a new head.
self.segments.appendleft(self.head() + self.direction)
if self.growth_pending > 0:
self.growth_pending -= 1
else:
# Remove tail.
self.segments.pop()
def grow(self):
"""Grow snake by one segment and speed up."""
self.growth_pending += 1
self.speed += SNAKE_SPEED_INCREMENT
def self_intersecting(self):
"""Is the snake currently self-intersecting?"""
it = iter(self)
head = next(it)
return head in it
class SnakeGame(object):
def __init__(self):
pygame.display.set_caption('PyGame Snake')
self.block_size = BLOCK_SIZE
self.window = pygame.display.set_mode(WORLD_SIZE * self.block_size)
self.screen = pygame.display.get_surface()
self.clock = pygame.time.Clock()
self.font = pygame.font.Font('freesansbold.ttf', 20)
self.world = Rect((0, 0), WORLD_SIZE)
self.reset()
def reset(self):
"""Start a new game."""
self.playing = True
self.next_direction = DIRECTION_UP
self.score = 0
self.snake = Snake(self.world.center, SNAKE_START_LENGTH)
self.food = set()
self.add_food()
def add_food(self):
"""Ensure that there is at least one piece of food.
(And, with small probability, more than one.)
"""
while not (self.food and randrange(4)):
food = Vector(map(randrange, self.world.bottomright))
if food not in self.food and food not in self.snake:
self.food.add(food)
def input(self, e):
"""Process keyboard event e."""
if e.key in KEY_DIRECTION:
self.next_direction = KEY_DIRECTION[e.key]
elif e.key == K_SPACE and not self.playing:
self.reset()
def update(self, dt):
"""Update the game by dt seconds."""
self.snake.update(dt, self.next_direction)
# If snake hits a food block, then consume the food, add new
# food and grow the snake.
head = self.snake.head()
if head in self.food:
self.food.remove(head)
self.add_food()
self.snake.grow()
self.score += len(self.snake) * SEGMENT_SCORE
# If snake collides with self or the screen boundaries, then
# it's game over.
if self.snake.self_intersecting() or not self.world.collidepoint(self.snake.head()):
self.playing = False
def block(self, p):
"""Return the screen rectangle corresponding to the position p."""
return Rect(p * self.block_size, DIRECTION_DR * self.block_size)
def draw_text(self, text, p):
"""Draw text at position p."""
self.screen.blit(self.font.render(text, 1, TEXT_COLOR), p)
def draw(self):
"""Draw game (while playing)."""
self.screen.fill(BACKGROUND_COLOR)
for p in self.snake:
pygame.draw.rect(self.screen, SNAKE_COLOR, self.block(p))
for f in self.food:
pygame.draw.rect(self.screen, FOOD_COLOR, self.block(f))
self.draw_text("Score: {}".format(self.score), (20, 20))
def draw_death(self):
"""Draw game (after game over)."""
self.screen.fill(DEATH_COLOR)
self.draw_text("Game over! Press Space to start a new game", (20, 150))
self.draw_text("Your score is: {}".format(self.score), (140, 180))
def play(self):
"""Play game until the QUIT event is received."""
while True:
dt = self.clock.tick(FPS) / 1000.0 # convert to seconds
for e in pygame.event.get():
if e.type == QUIT:
return
elif e.type == KEYUP:
self.input(e)
if self.playing:
self.update(dt)
self.draw()
else:
self.draw_death()
pygame.display.flip()
if __name__ == '__main__':
pygame.init()
SnakeGame().play()
pygame.quit()
after some thinking I managed to adapt the code so the snake can cross the screen boundaries without bugs. It wasn't actually that difficult after all. Those who are interested can see the code below:
from collections import deque
from itertools import *
import pygame
from random import randrange
import sys
from pygame.locals import *
class Vector(tuple):
"""A tuple that supports some vector operations.
>>> v, w = Vector((1, 2)), Vector((3, 4))
>>> v + w, w - v, v * 10, 100 * v, -v
((4, 6), (2, 2), (10, 20), (100, 200), (-1, -2))
"""
def __add__(self, other): return Vector(v + w for v, w in zip(self, other))
def __radd__(self, other): return Vector(w + v for v, w in zip(self, other))
def __sub__(self, other): return Vector(v - w for v, w in zip(self, other))
def __rsub__(self, other): return Vector(w - v for v, w in zip(self, other))
def __mul__(self, s): return Vector(v * s for v in self)
def __rmul__(self, s): return Vector(v * s for v in self)
def __neg__(self): return -1 * self
FPS = 60 # Game frames per second
SEGMENT_SCORE = 50 # Score per segment
SNAKE_SPEED_INITIAL = 4.0 # Initial snake speed (squares per second)
SNAKE_SPEED_INCREMENT = 0.25 # Snake speeds up this much each time it grows
SNAKE_START_LENGTH = 4 # Initial snake length in segments
WORLD_SIZE = Vector((20, 20)) # World size, in blocks
BLOCK_SIZE = 24 # Block size, in pixels
WORLD_BOUNDARIES = False
BACKGROUND_COLOR = 45, 45, 45
SNAKE_COLOR = 0, 255, 0
FOOD_COLOR = 255, 0, 0
DEATH_COLOR = 255, 0, 0
TEXT_COLOR = 255, 255, 255
DIRECTION_UP = Vector(( 0, -1))
DIRECTION_DOWN = Vector(( 0, 1))
DIRECTION_LEFT = Vector((-1, 0))
DIRECTION_RIGHT = Vector(( 1, 0))
DIRECTION_DR = DIRECTION_DOWN + DIRECTION_RIGHT
# Map from PyGame key event to the corresponding direction.
KEY_DIRECTION = {
K_w: DIRECTION_UP, K_UP: DIRECTION_UP,
K_s: DIRECTION_DOWN, K_DOWN: DIRECTION_DOWN,
K_a: DIRECTION_LEFT, K_LEFT: DIRECTION_LEFT,
K_d: DIRECTION_RIGHT, K_RIGHT: DIRECTION_RIGHT,
}
class Snake(object):
def __init__(self, start, start_length):
self.speed = SNAKE_SPEED_INITIAL # Speed in squares per second.
self.timer = 1.0 / self.speed # Time remaining to next movement.
self.growth_pending = 0 # Number of segments still to grow.
self.direction = DIRECTION_UP # Current movement direction.
self.segments = deque([start - self.direction * i
for i in xrange(start_length)])
def __iter__(self):
return iter(self.segments)
def __len__(self):
return len(self.segments)
def change_direction(self, direction):
"""Update the direction of the snake."""
# Moving in the opposite direction of current movement is not allowed.
if self.direction != -direction:
self.direction = direction
def head(self):
"""Return the position of the snake's head."""
return self.segments[0]
def tail(self):
"""Return the tail of the snake."""
return deque(islice(self.segments, 1, None))
def update(self, dt, direction):
"""Update the snake by dt seconds and possibly set direction."""
self.timer -= dt
if self.timer > 0:
# Nothing to do yet.
return
# Moving in the opposite direction of current movement is not allowed.
if self.direction != -direction:
self.direction = direction
self.timer += 1 / self.speed
'''************************************************************************************
***************************************************************************************
***************************************************************************************'''
# Add a new head.
if not WORLD_BOUNDARIES:
head = self.head()
if self.direction == DIRECTION_DOWN and head[1] == WORLD_SIZE[1]-1:
self.segments.appendleft(Vector((head[0], 0)))
elif self.direction == DIRECTION_UP and head[1] == 0:
self.segments.appendleft(Vector((head[0], WORLD_SIZE[1]-1)))
elif self.direction == DIRECTION_RIGHT and head[0] == WORLD_SIZE[0]-1:
self.segments.appendleft(Vector((0, head[1])))
elif self.direction == DIRECTION_LEFT and head[0] == 0:
self.segments.appendleft(Vector((WORLD_SIZE[0]-1, head[1])))
else: self.segments.appendleft(self.head() + self.direction)
else: self.segments.appendleft(self.head() + self.direction)
'''************************************************************************************
***************************************************************************************
***************************************************************************************'''
if self.growth_pending > 0:
self.growth_pending -= 1
else:
# Remove tail.
self.segments.pop()
def grow(self):
"""Grow snake by one segment and speed up."""
self.growth_pending += 1
self.speed += SNAKE_SPEED_INCREMENT
def self_intersecting(self):
"""Is the snake currently self-intersecting?"""
it = iter(self)
head = next(it)
return head in it
class SnakeGame(object):
def __init__(self):
pygame.display.set_caption('PyGame Snake')
self.block_size = BLOCK_SIZE
self.window = pygame.display.set_mode(WORLD_SIZE * self.block_size)
self.screen = pygame.display.get_surface()
self.clock = pygame.time.Clock()
self.font = pygame.font.Font('freesansbold.ttf', 20)
self.world = Rect((0, 0), WORLD_SIZE)
self.reset()
def reset(self):
"""Start a new game."""
self.playing = True
self.next_direction = DIRECTION_UP
self.score = 0
self.snake = Snake(self.world.center, SNAKE_START_LENGTH)
self.food = set()
self.add_food()
def add_food(self):
"""Ensure that there is at least one piece of food.
(And, with small probability, more than one.)
"""
while not (self.food and randrange(4)):
food = Vector(map(randrange, self.world.bottomright))
if food not in self.food and food not in self.snake:
self.food.add(food)
def input(self, e):
"""Process keyboard event e."""
if e.key in KEY_DIRECTION:
self.next_direction = KEY_DIRECTION[e.key]
elif e.key == K_SPACE and not self.playing:
self.reset()
def update(self, dt):
"""Update the game by dt seconds."""
self.snake.update(dt, self.next_direction)
# If snake hits a food block, then consume the food, add new
# food and grow the snake.
head = self.snake.head()
if head in self.food:
self.food.remove(head)
self.add_food()
self.snake.grow()
self.score += len(self.snake) * SEGMENT_SCORE
# If snake collides with self or the screen boundaries, then
# it's game over.
if self.snake.self_intersecting() or not self.world.collidepoint(self.snake.head()):
self.playing = False
def block(self, p):
"""Return the screen rectangle corresponding to the position p."""
return Rect(p * self.block_size, DIRECTION_DR * self.block_size)
def draw_text(self, text, p):
"""Draw text at position p."""
self.screen.blit(self.font.render(text, 1, TEXT_COLOR), p)
def draw(self):
"""Draw game (while playing)."""
self.screen.fill(BACKGROUND_COLOR)
for p in self.snake:
pygame.draw.rect(self.screen, SNAKE_COLOR, self.block(p))
for f in self.food:
pygame.draw.rect(self.screen, FOOD_COLOR, self.block(f))
self.draw_text("Score: {}".format(self.score), (20, 20))
def draw_death(self):
"""Draw game (after game over)."""
self.screen.fill(DEATH_COLOR)
self.draw_text("Game over! Press Space to start a new game", (20, 150))
self.draw_text("Your score is: {}".format(self.score), (140, 180))
def play(self):
"""Play game until the QUIT event is received."""
while True:
dt = self.clock.tick(FPS) / 1000.0 # convert to seconds
for e in pygame.event.get():
if e.type == QUIT:
return
elif e.type == KEYUP:
self.input(e)
if self.playing:
self.update(dt)
self.draw()
else:
self.draw_death()
pygame.display.flip()
if __name__ == '__main__':
pygame.init()
SnakeGame().play()
pygame.quit()