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Я столкнулся с проблемой в своем проекте и мог бы воспользоваться некоторой помощью, чтобы выяснить, что я делаю неправильно.

 import random

# Define some colors
black    = (   0,   0,   0)
white    = ( 255, 255, 255)
green    = (   0, 255,   0)
red      = ( 255,   0,   0)

class caterpillar:
    def __init__(self, x, y):
        self.face_xcoord = x
        self.face_ycoord = y
        self.body = segment_queue()
        t = random.randrange(0,2)
        if t == 0:
            self.travel_direction = 'left'
        else:
            self.travel_direction = 'right'
        
    def display_caterpillar(self, screen):
        self.draw_face(screen)
        self.draw_body(screen)

    def draw_face(self, screen):
        x = self.face_xcoord 
        y = self.face_ycoord
        pygame.draw.ellipse(screen,red,[x, y, 40, 45])
        pygame.draw.ellipse(screen,black,[x 6, y 10, 10, 15])
        pygame.draw.ellipse(screen,black,[x 24, y 10, 10, 15])
        pygame.draw.line(screen,black, (x 11, y), (x 9, y-10), 3)
        pygame.draw.line(screen,black, (x 24, y), (x 26, y-10), 3)
        
    def draw_body(self, screen):
        # traverse the segment queue
        current_node = self.body.head
        while current_node is not None:
           current_node.draw_segment(screen) 
           current_node = current_node.next 

####### you need to complete these two methods

    def grow(self):
        if self.body.length == 0:
            if self.travel_direction == 'left':
                self.body.addSegment(self.face_xcoord   40, self.face_ycoord)
            elif self.travel_direction == 'right':
                self.body.addSegment(self.face_xcoord - 35, self.face_ycoord)
        else:
            self.body.addSegment(self.body.last, self.face_ycoord)

        # if body is empty new segment should be placed relative to head
        # else find x and y coordinates for current last body segment
        # call addSegment() method on self.body with correct location parameters

    def move(self):
        return
        # check the direction of movement
        # move head forwards by 2
        # move body parts forwards by 2
        
        
class segment_queue:
    def __init__(self):
        self.length = 0
        self.head = None
        self.last = None
      
    def isEmpty(self):
        return self.length == 0
    
####### you need to complete this method
      
    def addSegment(self, x, y):
        node = body_segment(x, y)
        if self.length == 0:
            self.head = self.last = node
        else:
            last = self.last
            last.next = node
            self.last = node
            self.length = self.length   1
        # create a new body_segment node, with parameters x and y     
        # if segment queue is empty, the new node is both head and last
        # else, find the last node and then append the new node to the end of the queue
        # increment length of the segment queue
 
  
class body_segment:
    def __init__(self, x, y):
        self.xcoord = x
        self.ycoord = y
        self.next = None
        
    def draw_segment(self, screen):
        x = self.xcoord
        y = self.ycoord
        pygame.draw.ellipse(screen,green,[x, y, 35, 40])
        pygame.draw.line(screen,black, (x 8, y 35), (x 8, y 45), 3)
        pygame.draw.line(screen,black, (x 24, y 35), (x 24, y 45), 3) 
  

Следующий файл

 import catclass
 
# Define some colors
black     = (   0,   0,   0)
white     = ( 255, 255, 255)
green     = (   0, 255,   0)
red       = ( 255,   0,   0)
lightblue = (   0,   0,  255)
 

# Initialize pygame
pygame.init()
  
# Set the height and width of the screen
size=[1000,400]
screen=pygame.display.set_mode(size)
 
# Set title of screen
pygame.display.set_caption("Caterpillar")

# Function to draw background scene
def draw_background():
   screen.fill(black)
   pygame.draw.rect(screen,green,[0, 300, 1000, 100])
   pygame.draw.rect(screen,lightblue,[0, 0, 1000, 300])
   pygame.draw.ellipse(screen,white,[50, 80, 100, 60])
   pygame.draw.ellipse(screen,white,[120, 60, 180, 80])
   pygame.draw.ellipse(screen,white,[700, 80, 150, 60])

# Create a caterpillar at a particular location
mycaterpillar = catclass.caterpillar(500, 250)
 
# Loop until the user clicks the close button.
done=False
# Used to manage how fast the screen updates
clock=pygame.time.Clock()

######################################
# -------- Main Program Loop -----------
while done==False:
    for event in pygame.event.get(): # User did something
        if event.type == pygame.QUIT: # If user clicked close
            done=True # Flag that we are done so we exit this loop
        if event.type == pygame.KEYDOWN: # If user wants to perform an action
            # Figure out which action to perform
            if event.key == pygame.K_SPACE:
                mycaterpillar.grow()
            if event.key == pygame.K_m:
                mycaterpillar.move()
                
    # Draw the background scene
    draw_background()
    # Draw the caterpillar
    mycaterpillar.display_caterpillar(screen)
     
    # Limit to 20 frames per second
    clock.tick(10)
 
    # Go ahead and update the screen with what we've drawn.
    pygame.display.flip()
     
# If you forget this line, the program will 'hang' on exit.
pygame.quit ()
  

Проблема, с которой я сталкиваюсь, заключается в том, что я не могу понять, почему моя гусеница не увеличивает более одного сегмента тела при вызове grow() метода. В настоящее время при вызове функции, которая находится в if инструкции, увеличивается только один сегмент. else Оператор, похоже, ничего не делает.

Несколько вещей, которые я заметил в вашем коде:

• В addSegment методе значение length никогда не превышает нуля
• В grow методе добавляется только первый сегмент. Другие сегменты игнорируются.
• Как упоминал @Kingsley, вы создаете новый сегмент с объектом вместо координаты x

Внесите эти изменения в caterpillar класс:

 def grow(self):
    if self.body.length == 0:  # first segment
        if self.travel_direction == 'left':
            self.body.addSegment(self.face_xcoord   40, self.face_ycoord)
        elif self.travel_direction == 'right':
            self.body.addSegment(self.face_xcoord - 35, self.face_ycoord)
    else:  # other segs
        if self.travel_direction == 'left':
            self.body.addSegment(self.body.last.xcoord   40, self.face_ycoord)
        elif self.travel_direction == 'right':
            self.body.addSegment(self.body.last.xcoord - 35, self.face_ycoord)
  

 def addSegment(self, x, y):
    node = body_segment(x, y)
    if self.length == 0:
        self.head = self.last = node
        self.length  = 1  # add this line
    else:
        last = self.last
        last.next = node
        self.last = node
        self.length = self.length   1
  

Вывод