Pygame Map Editor(almost working)

import pygame
from pygame.locals import *
from math import ceil

tile_files = [
    "../pictures/tiles1.png"
]
tile_files = [pygame.image.load(f) for f in tile_files]

class Tile(pygame.sprite.Sprite):
    """ Create 32x32 Tile Sprite """
    def __init__(self, i, file_index, tile_x, tile_y):
        pygame.sprite.Sprite.__init__(self)
        self.tile_index = i
        self.image = tile_files[file_index].subsurface((tile_x*32, tile_y*32, 32, 32))
        self.image = self.image.convert_alpha()
        self.rect = self.image.get_rect()
        self.rect.x = (i%8)*37+4
        self.rect.y = (i/8)*37+4
class Scroll_Button(pygame.sprite.Sprite):
    """ Create Tile Area Scrolling Button """
    def __init__(self, image, btn_x, btn_y, scroll_dir):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.image.load(image)
        self.rect = self.image.get_rect()
        self.rect.x = btn_x
        self.rect.y = btn_y
        self.scroll_dir = scroll_dir


class Editor:
    """ Main Map Editor Class """
    tile_area = None
    buttons = None
    selected_tile = None
    def __init__(self):
        """ Init a window and surfaces """
        pygame.init()
        pygame.display.set_caption("Map Editor")
        self.map_preview_font = pygame.font.Font(None, 128)
        self.running = True
        self.clock = pygame.time.Clock()
        self.screen = pygame.display.set_mode((1324,600), DOUBLEBUF)
        self.map_preview = pygame.Surface((1024,600))
        self.button_panel = pygame.Surface((300,30)).convert()
        self.screen.fill((255,255,255))
        self.load_tiles()
        self.loop()
    def load_tiles(self):
        """ Get all tiles and add them to sprite group, create 2 scrolling buttons and mouse object """
        self.tiles = pygame.sprite.Group()
        tiles = []
        num_of_tiles = 0

        # ~ # Count tiles and create list # ~ #
        for i, f in enumerate(tile_files):
            _, _, width, height = f.get_rect()
            num_of_tiles += width/32 * height/32
            tiles += [(i, x, y) for y in range(height/32) for x in range(width/32)]

        # ~ # Create Tile Area And Add Tiles + Scrolling Offset/Limit # ~ #
        height = 37*ceil(float(num_of_tiles)/8)+10
        self.tile_area = pygame.Surface((300, height))
        self.scroll_offset = 0
        self.scroll_limit = -height+570
        for j, (i, x, y) in enumerate(tiles):
            self.tiles.add(Tile(j, i, x, y))

        # ~ # Create Scrolling Buttons # ~ #
        self.buttons = pygame.sprite.Group()
        btn_up = Scroll_Button("../pictures/btn_up.png", 0, 570, 5)
        self.buttons.add(btn_up)
        btn_down = Scroll_Button("../pictures/btn_down.png", 100, 570, -5)
        self.buttons.add(btn_down)

        # ~ # Mouse # ~ #
        self.mouse = pygame.sprite.Sprite()
        self.mouse.rect = pygame.Rect((0,0,0,0))
    def get_events(self):
        """ Check for pygame events """
        for event in pygame.event.get():
            # ~ # Quit Editor # ~ #
            if event.type==QUIT or (event.type==KEYDOWN and event.key==K_ESCAPE):
                self.running = False
            # ~ # Select Tile # ~ #
            if event.type==MOUSEBUTTONDOWN:
                clicked = pygame.sprite.spritecollide(self.mouse, self.tiles, False)
                for t in clicked:
                    self.selected_tile = t
                    print t.tile_index

        # ~ # Scrolling Tile Area # ~ #
        scroll = pygame.sprite.spritecollide(self.mouse, self.buttons, False)
        for b in scroll:
            if self.scroll_offset >= 0 and b.scroll_dir > 0:
                continue
            elif self.scroll_offset <= self.scroll_limit and b.scroll_dir < 0:
                continue
            self.scroll_offset+=b.scroll_dir
            for s in self.tiles:
                s.rect.y+=b.scroll_dir
    def loop(self):
        """ Main program loop, display everything 60 times per second """
        while self.running:
            # ~ # Update Mouse Sprite # ~ #
            pos = pygame.mouse.get_pos()
            self.mouse.rect.x = pos[0]
            self.mouse.rect.y = pos[1]

            # ~ # Events # ~ #
            self.get_events()

            # ~ # Show map preview # ~ #
            self.screen.fill((200,200,200))
            self.screen.blit(self.map_preview, (300, 0))
            txt2 = self.map_preview_font.render("Map Preview", True, (255,255,255))
            self.map_preview.blit(txt2, (300,236))

            # ~ # Show tile menu # ~ #
            self.tile_area.fill((0,0,0))
            self.tiles.draw(self.tile_area)
            self.screen.blit(self.tile_area, (0, 0))
            self.button_panel.fill((200,200,200))
            self.screen.blit(self.button_panel, (0, 570))
            self.buttons.draw(self.screen)
            pygame.draw.line(self.screen, (255,0,0), (300,0), (300, 600), 1)

            self.clock.tick(60)
            pygame.display.update()
if __name__=="__main__":
    editor = Editor()