A moving rectangle becomes stuck after hitting the edge of the window - python-3.x

Question

I created a rectangle in the middle of the window, and used key 'w', 's', 'a', 'd', to move it. My problem is every time the rectangle hits the edge of the window is becomes stuck and cannot move any more.
import pygame, sys, time
from pygame.locals import *
class Tile:
bcolor = pygame.Color('black')
rcolor = pygame.Color('white')
def __init__(self, surface):
self.surface = surface
self.size = 30
self.x = self.surface.get_width()//2 - self.size//2
self.y = self.surface.get_height()//2 - self.size//2
self.rect = pygame.Rect(self.x, self.y, self.size, self.size)
self.speed = 10
self.rcolor = Tile.rcolor
self.bcolor = Tile.bcolor
def draw(self):
pygame.draw.rect(self.surface, self.rcolor, self.rect)
def moveup(self):
if self.rect.top < self.speed:
self.speed = self.rect.top
self.rect.move_ip(0, -self.speed)
def movedown(self):
maxbottom = self.surface.get_height()
if maxbottom - self.rect.bottom < self.speed:
self.speed = maxbottom - self.rect.bottom
self.rect.move_ip(0,self.speed)
def moveleft(self):
if self.rect.left < self.speed:
self.speed = self.rect.left
self.rect.move_ip(-self.speed, 0)
def moveright(self):
maxright = self.surface.get_width()
if maxright - self.rect.right < self.speed:
self.speed = maxright - self.rect.right
self.rect.move_ip(self.speed, 0)
def handlekeydown(self, key):
if key == K_w:
self.moveup()
if key == K_s:
self.movedown()
if key == K_a:
self.moveleft()
if key == K_d:
self.moveright()
def update(self):
self.surface.fill(self.bcolor)
self.draw()
def main():
pygame.init()
pygame.key.set_repeat(20, 20)
surfacesize = (500,400)
title = 'Practice'
framedelay = 0.02
surface = pygame.display.set_mode(surfacesize, 0, 0)
pygame.display.set_caption(title)
tile = Tile(surface)
gameover = False
tile.draw()
pygame.display.update()
while True:
for event in pygame.event.get():
if event.type == QUIT:
pygame.quit()
sys.exit()
if event.type == KEYDOWN and not gameover:
tile.handlekeydown(event.key)
tile.update()
pygame.display.update()
time.sleep(framedelay)
main()

Answer 1

Just look at this piece of code:
def moveup(self):
if self.rect.top < self.speed:
self.speed = self.rect.top
self.rect.move_ip(0, -self.speed)
Once you move to the top of the screen, self.rect.top becomes 0, which is smaller than self.speed, so the condition of the if statement is True and in the next line you set self.speed to 0, hence all your move_ip calls won't move the Rect (because self.speed is now 0).
If you want to prevent the Rect from leaving the screen, better just use clamp_ip:
...
def moveup(self):
self.rect.move_ip(0, -self.speed)
def movedown(self):
self.rect.move_ip(0,self.speed)
def moveleft(self):
self.rect.move_ip(-self.speed, 0)
def moveright(self):
self.rect.move_ip(self.speed, 0)
def handlekeydown(self, key):
if key == K_w:
self.moveup()
if key == K_s:
self.movedown()
if key == K_a:
self.moveleft()
if key == K_d:
self.moveright()
self.rect.clamp_ip(pygame.display.get_surface().get_rect())
...
(There are some other issues with your code, but that's another topic.)