Example Pygame Grid Structure

import pygame

# Simple boiler plate
class Scene:
    def __init__(self, control):
        self.control = control

    def on_draw(self, surface):
        pass

    def on_event(self, event):
        pass

    def on_update(self, delta):
        pass

class SceneHandler:
    def __init__(self):
        self.current = None
        self.next_ = None

    def push(self, scene):
        self.next_ = scene

    def update(self):
        if self.next_:
            self.current = self.next_
            self.next_ = None

        return self.current

class SceneControl:
    def __init__(self, caption, width, height, flags=0, fps=60):
        pygame.display.set_caption(caption)
        self.display = pygame.display.set_mode((width, height), flags)
        self.rect = self.display.get_rect()
        self.clock = pygame.time.Clock()
        self.running = True
        self.delta = 0
        self.fps = fps

        self.scene = SceneHandler()

    def loop(self):
        if self.scene.current:
            while self.running:
                scene = self.scene.update()
                for event in pygame.event.get():
                    if event.type != pygame.QUIT:
                        scene.on_event(event)
                    else:
                        self.running = False

                scene.on_update(self.delta)
                scene.on_draw(self.display)
                pygame.display.flip()
                self.delta = self.clock.tick(self.fps)/1000

    def run(self, scene):
        self.scene.current = scene
        self.loop()

class Grid:
    def __init__(self, rect, cut, gap=(0, 0)):
        self.rect = rect
        self.cut = cut
        self.gap = gap
        self.slice = cut[0] + gap[0], cut[1] + gap[1]
        self.blocks = self.get_blocks()

    def get_blocks(self):
        blocks = []
        for y in range(self.rect.y, self.rect.h, self.slice[1]):
            xblock = []
            for x in range(self.rect.x, self.rect.w, self.slice[0]):
                xblock.append(pygame.Rect((x, y), self.cut))
            blocks.append(xblock)

        return blocks

    def get_cells(self):
        return len(self.blocks[0]), len(self.blocks)

    def get_empty_blocks(self):
        w, h = self.get_cells()
        return [[None for _ in range(w)] for _ in range(h)]

    def collide(self, mpos):
        x, y = self.get_coords(mpos)
        if self.blocks[y][x].collidepoint(mpos):
            return self.blocks[y][x].copy()

    def collision_point(self, mpos):
        x, y = self.get_coords(mpos)
        if self.blocks[y][x].collidepoint(mpos):
            return x, y

    def get_coords(self, mpos):
        x = (mpos[0] - self.rect.x) // self.slice[0]
        y = (mpos[1] - self.rect.y) // self.slice[1]
        return x, y

    def draw_outline(self, surface):
        for yblock in self.blocks:
            for rect in yblock:
                pygame.draw.rect(surface, 'lawngreen', rect, 1)

class Game(Scene):
    def __init__(self, control):
        super().__init__(control)
        self.grid = Grid(self.control.rect.inflate(-20, -20), (20, 20))
        self.hover = None
        self.blocks = self.grid.get_empty_blocks()
        self.toggle_grid = False

    def on_draw(self, surface):
        surface.fill('black')
        if self.toggle_grid:
            self.grid.draw_outline(surface)

        for blocks in self.blocks:
            for rect in blocks:
                if rect:
                    surface.fill('dodgerblue', rect)

    def on_event(self, event):
        if event.type == pygame.MOUSEBUTTONDOWN:
            if event.button == 1:
                point = self.grid.collision_point(event.pos)
                if point:
                    x, y = point
                    if self.blocks[y][x]:
                        self.blocks[y][x] = None
                    else:
                        self.blocks[y][x] = self.grid.collide(event.pos)
        elif event.type == pygame.KEYDOWN:
            if event.key == pygame.K_SPACE:
                self.toggle_grid = not self.toggle_grid

if __name__ == "__main__":
    pygame.init()
    control = SceneControl("Grid Example", 800, 600)
    control.run(Game(control))
    pygame.quit()