Player movement

Question

I wrote this simple code that draws and then lets you move a rectangle, but even after I change the coordinates of the rectangle by calling the move_player_x_ function, it doesn't move at all. I don't understand why. I came here looking for clarification and a detailed solution to my problem.

Here's the code:

import pygame

white = (255, 255, 255)
black = (0, 0, 0)

class Game():
    width = 800
    height = 600
    screen = pygame.display.set_mode((width, height))

    def __init__(self):
        pass
    def fill_screen(self, color):
        self.color = color
        self.screen.fill(self.color)

    def update_method(self):
        pygame.display.update()

game = Game()


class Player(pygame.sprite.Sprite):
    lead_x = game.width/2
    lead_y = game.height/2
    lead_x_change = 0
    lead_y_change = 0
    velocity = 0.2
    block_size = 10
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)

    def move_player_x_left(self):
        self.lead_x_change += -self.velocity

    def move_player_x_right(self):
        self.lead_x_change += self.velocity

    def move_player_y_up(self):
        self.lead_y_change += -self.velocity

    def move_player_y_down(self):
        self.lead_y_change += self.velocity

    def draw_player(self):
        pygame.draw.rect(game.screen, black, [self.lead_x, self.lead_y, self.block_size, self.block_size])

    def key_up_x_stop(self):
        self.lead_x = 0

    def key_up_y_stop(self):
        self.lead_y = 0

    def constant_x_movement(self):
        self.lead_x += self.lead_x_change

    def constant_y_movement(self):
        self.lead_y += self.lead_y_change


player = Player()

exitGame = False
while not exitGame:
    game.fill_screen(white)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            exitGame = True
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_w:
                    player.move_player_y_up()
                if event.key == pygame.K_s:
                    player.move_player_y_down()
                if event.key == pygame.K_a:
                    player.move_player_x_left()
                if event.key == pygame.K_d:
                    player.move_player_x_right()

            if event.type == pygame.KEYUP:
                if event.key == pygame.K_w or event.key == pygame.K_s:
                    player.key_up_y_stop()
                if event.key == pygame.K_a or event.key == pygame.K_d:
                    player.key_up_x_stop()
    player.constant_x_movement()
    player.constant_y_movement()        

    player.draw_player()
    game.update_method()
pygame.quit()
quit()

Answer 1

The code in the event loop is not indented correctly. Here's a corrected version:

while not exitGame:
    game.fill_screen(white)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            exitGame = True
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_w:
                player.move_player_y_up()
            if event.key == pygame.K_s:
                player.move_player_y_down()
            if event.key == pygame.K_a:
                player.move_player_x_left()
            if event.key == pygame.K_d:
                player.move_player_x_right()
        if event.type == pygame.KEYUP:
            if event.key == pygame.K_w or event.key == pygame.K_s:
                player.key_up_y_stop()
            if event.key == pygame.K_a or event.key == pygame.K_d:
                player.key_up_x_stop()

Also, in the ...stop methods, you have to set lead_x_change and lead_y_change to 0 not lead_x and lead_y .

def key_up_x_stop(self):
    self.lead_x_change = 0

def key_up_y_stop(self):
    self.lead_y_change = 0

Answer 2

I edited your code, i added a function in the player object move_player with local booleans bUp,bDown,bLeft,bRight . If python had enumerations, it would be so much better. Any how, on event KEY DOWN and KEY UP, they toggle these booleans in the player. after the input is calculated and these booleans are toggled/set, it called move_player() in player object that checks its booleans and sets a while loop while one is true and adds velocity in the respected location and redraws player. Here the source i got for you...

import pygame

white = (255, 255, 255)
black = (0, 0, 0)

class Game():
    width = 800
    height = 600
    screen = pygame.display.set_mode((width, height))
    def __init__(self):
        pass
    def fill_screen(self, color):
        self.color = color
        self.screen.fill(self.color)

    def update_method(self):
        pygame.display.update()

class Player(pygame.sprite.Sprite):
    lead_x = 800/2
    lead_y = 600/2
    velocity = 0.002
    block_size = 10

    bUp = false 
    bDown = false 
    bLeft = false 
    bRight = false

    def __init__(self):
        pygame.sprite.Sprite.__init__(self)

    def draw_player(self):
        pygame.draw.rect(game.screen, black, [self.lead_x, self.lead_y, self.block_size, self.block_size])

    def move_player(self):
        while bLeft:
            self.lead_x += -self.velocity
            self.draw_player()
        while bRight:
            self.lead_x += self.velocity
            self.draw_player()
        while bUp:
            self.lead_y += -self.velocity
            self.draw_player()
        while bDown:
            self.lead_y += self.velocity
            self.draw_player()

game = Game()
player = Player()

exitGame = False
while not exitGame:
    game.fill_screen(white)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            exitGame = True
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_w:
                player.bUp = true
            if event.key == pygame.K_s:
                player.bDown = true 
            if event.key == pygame.K_d:
                player.bRight = true
            if event.key == pygame.K_a:
                player.bLeft = true
        elif event.type == pygame.KEYUP:
            if event.key == pygame.K_w:
                player.bUp = false
            if event.key == pygame.K_s:
                player.bDown = false 
            if event.key == pygame.K_d:
                player.bRight = false
            if event.key == pygame.K_a:
                player.bLeft = false
    player.move_player()
    game.update_method()
pygame.quit()
quit()