Python中赋值前调用的变量

Question

我遇到了一个问题，我需要在多个函数中调用一些变量，但无法在game_lop((函数中声明它们。这些变量在game_oop函数之外被调用，但这些变量也被调用到其他函数中。如何在game_oop函数和所有其他调用变量的函数中获取要调用的变量？

请参阅以下代码：

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 = (0,0,0)
white = (255, 255, 255)
red = (200, 0, 0)
bright_red = (255,0,0)
block_color = (53,115,255)
green = (0,200,0)
bright_green = (0,255,0)

# 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), True, (255, 255, 255))
screen.blit(score, (x, y))


def game_over_text():
over_text = over_font.render("GAME OVER", True, (255, 255, 255))
screen.blit(over_text, (200, 250))


def player(x, y):
screen.blit(playerImg, (x, y))


def ship(x, y, i):
screen.blit(shipImg[i], (x, 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, y, 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, ac, (x, y, w, h))
#check for a click
if click[0] == 1 and action!=None:
action()
else:
pygame.draw.rect(screen, ic, (x, y, w, 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, 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, 450, 100, 50, 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, 0))
# Background Image
screen.blit(background, (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], cannonX, 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], shipY[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()

Answer 1

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)

Answer 2

您引用的是在函数外部声明的变量。你的函数不知道它们的存在，因此它们通过了错误。

要在函数中使用这些变量，需要将它们声明为全局变量。

这就是你需要做的

def game_loop():
global playerX
global playerX_change
global cannonX
global cannonY
global cannon_state

你也可以对的其他功能这样做