如何解决Python 赋值前调用的变量
我有一个问题，我需要在多个函数中调用一些变量，但无法在 game_loop() 函数中声明它们。变量在 game_loop 函数之外被调用，但变量也被调用到其他函数中。如何让变量在 game_loop 函数和所有其他调用它们的函数中调用？
请看下面的代码：
import math
import random
import pygame
from pygame import mixer
# Intialize the pygame
pygame.init()
# next setup the display
display_width = 800
display_height = 600
screen = pygame.display.set_mode((800,600))
# Background
background = pygame.image.load('waterbackground.jpg')
# game clock to time frames per second
clock = pygame.time.Clock()
# Sound
mixer.music.load("ocean.wav")
mixer.music.play(-1)
# setup colors needed in the game
black = (0,0)
white = (255,255,255)
red = (200,0)
bright_red = (255,0)
block_color = (53,115,255)
green = (0,200,0)
bright_green = (0,0)
# Caption and Icon
pygame.display.set_caption("Pirate War")
icon = pygame.image.load('pirateship.png')
pygame.display.set_icon(icon)
# cannon
cannonImg = pygame.image.load('cannonball.png')
cannonX = 0
cannonY = 480
cannonX_change = 0
cannonY_change = 10
cannon_state = "ready"
# Player
playerImg = pygame.image.load('cannon.png')
playerX = 370
playerY = 480
playerX_change = 0
# score
score_value = 0
# ship
shipImg = []
shipX = []
shipY = []
shipX_change = []
shipY_change = []
num_of_ships = 6
for i in range(num_of_ships):
shipImg.append(pygame.image.load('pirateship.png'))
shipX.append(random.randint(0,736))
shipY.append(random.randint(50,150))
shipX_change.append(4)
shipY_change.append(40)
font = pygame.font.Font('freesansbold.ttf',32)
textx = 10
testY = 10
# Game Over
over_font = pygame.font.Font('freesansbold.ttf',64)
# text object function called by message display function
def text_objects(text,font):
textSurface = font.render(text,True,black)
return textSurface,textSurface.get_rect()
def show_score(x,y):
score = font.render("score : " + str(score_value),(255,255))
screen.blit(score,(x,y))
def game_over_text():
over_text = over_font.render("GAME OVER",255))
screen.blit(over_text,(200,250))
def player(x,y):
screen.blit(playerImg,y))
def ship(x,y,i):
screen.blit(shipImg[i],y))
def fire_cannon(x,y):
global cannon_state
cannon_state = "fire"
screen.blit(cannonImg,(x + 16,y + 10))
def isCollision(shipX,shipY,cannonX,cannonY):
distance = math.sqrt(math.pow(shipX - cannonX,2) + (math.pow(shipY - cannonY,2)))
if distance < 27:
return True
else:
return False
def button(msg,x,w,h,ic,ac,action=None):
mouse = pygame.mouse.get_pos() # returns a list of [x,y]
click = pygame.mouse.get_pressed()
if x+w > mouse[0] > x and y+h > mouse[1] > y: #check is mouse over button
# redraw the rectange with active color when mouSEOver
pygame.draw.rect(screen,h))
#check for a click
if click[0] == 1 and action!=None:
action()
else:
pygame.draw.rect(screen,h))
# Now display text on top of button that was just redrawn
smallText = pygame.font.Font('freesansbold.ttf',20)
TextSurf,TextRect = text_objects(msg,smallText)
TextRect.center = ((x+(w/2)),(y+(h/2)))
screen.blit(TextSurf,TextRect)
def quitgame():
pygame.quit()
quit()
# start screen code
def game_intro():
intro = True
while intro:
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
quit()
screen.fill((0,0))
# Background Image
screen.blit(background,(0,0))
largeText = pygame.font.Font('freesansbold.ttf',115)
TextSurf,TextRect = text_objects("Pirate War",largeText)
TextRect.center = ((display_width/2),(display_height/2))
screen.blit(TextSurf,TextRect)
#add buttons to start screen
button("Go!",150,450,100,50,green,bright_green,game_loop)
button("Quit",550,red,bright_red,quitgame)
pygame.display.update()
clock.tick(15)
def game_loop():
# Game Loop
running = True
while running:
# RGB = Red,Green,Blue
screen.fill((0,0))
for event in pygame.event.get():
if event.type == pygame.QUIT:
running = False
# if keystroke is pressed check whether its right or left
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_LEFT:
playerX_change = -5
if event.key == pygame.K_RIGHT:
playerX_change = 5
if event.key == pygame.K_SPACE:
if cannon_state == "ready":
cannonSound = mixer.sound("cannon_x.wav")
cannonSound.play()
# Get the current x cordinate of the spaceship
cannonX = playerX
fire_cannon(cannonX,cannonY)
if event.type == pygame.KEYUP:
if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
playerX_change = 0
# 5 = 5 + -0.1 -> 5 = 5 - 0.1
# 5 = 5 + 0.1
playerX += playerX_change
if playerX <= 0:
playerX = 0
elif playerX >= 736:
playerX = 736
# ship Movement
for i in range(num_of_ships):
# Game Over
if shipY[i] > 440:
for j in range(num_of_ships):
shipY[j] = 2000
game_over_text()
break
shipX[i] += shipX_change[i]
if shipX[i] <= 0:
shipX_change[i] = 1 #######SHIP MOVEMENT
shipY[i] += shipY_change[i]
elif shipX[i] >= 736:
shipX_change[i] = -1 ######SHIP MOVEMENT
shipY[i] += shipY_change[i]
# Collision
collision = isCollision(shipX[i],shipY[i],cannonY)
if collision:
explosionSound = mixer.sound("explosion.wav")
explosionSound.play()
cannonY = 480
cannon_state = "ready"
score_value += 1
shipX[i] = random.randint(0,736)
shipY[i] = random.randint(50,150)
ship(shipX[i],i)
# cannon Movement
if cannonY <= 0:
cannonY = 480
cannon_state = "ready"
if cannon_state == "fire":
fire_cannon(cannonX,cannonY)
cannonY -= cannonY_change
player(playerX,playerY)
show_score(textx,testY)
pygame.display.update()
game_intro()
解决方法
如果您需要的是能够在函数中使用全局变量，那么您只需要关键字 global。
x = 0
def inc() :
global x
x += 1
inc()
print(x)
您指的是在函数外声明的变量。您的函数不知道它们存在，因此它们通过错误。
要在函数中使用这些变量，您需要将它们声明为全局变量。
这是你需要做的
def game_loop():
global playerX
global playerX_change
global cannonX
global cannonY
global cannon_state
您也可以对其他功能执行此操作
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