Part 10 - Saving and loading

Saving and loading is essential to almost every roguelike, but it can be a pain to manage if you don’t start early. By the end of this chapter, our game will be able to save and load one file to the disk, which you could easily expand to multiple saves if you wanted to. But before we get into that, let’s focus on our main game loop.

The engine.py file is about 250 lines long right now. In the grand scheme of things, that really isn’t that bad (I’ve worked on files that are 10,000 lines long), but let’s face it: a lot of what’s in there doesn’t need to be. Furthermore, the main function could be broken up into initialization and the main game loop, which will make saving and loading that much easier.

The first step is to move the initialization of the variables outside the main game loop as much as we can. We’ll create a few functions that will do things like create the player, create the map, and load variables like map_width and fov_algorithm. Let’s create a new folder called loader_functions, and put a new file in it called initialize_new_game.py.

Our first function in this new file will return the variables that are currently at the top of the main function. It looks like this:

import tcod as libtcod


def get_constants():
    window_title = 'Roguelike Tutorial Revised'

    screen_width = 80
    screen_height = 50

    bar_width = 20
    panel_height = 7
    panel_y = screen_height - panel_height

    message_x = bar_width + 2
    message_width = screen_width - bar_width - 2
    message_height = panel_height - 1

    map_width = 80
    map_height = 43

    room_max_size = 10
    room_min_size = 6
    max_rooms = 30

    fov_algorithm = 0
    fov_light_walls = True
    fov_radius = 10

    max_monsters_per_room = 3
    max_items_per_room = 2

    colors = {
        'dark_wall': libtcod.Color(0, 0, 100),
        'dark_ground': libtcod.Color(50, 50, 150),
        'light_wall': libtcod.Color(130, 110, 50),
        'light_ground': libtcod.Color(200, 180, 50)
    }

    constants = {
        'window_title': window_title,
        'screen_width': screen_width,
        'screen_height': screen_height,
        'bar_width': bar_width,
        'panel_height': panel_height,
        'panel_y': panel_y,
        'message_x': message_x,
        'message_width': message_width,
        'message_height': message_height,
        'map_width': map_width,
        'map_height': map_height,
        'room_max_size': room_max_size,
        'room_min_size': room_min_size,
        'max_rooms': max_rooms,
        'fov_algorithm': fov_algorithm,
        'fov_light_walls': fov_light_walls,
        'fov_radius': fov_radius,
        'max_monsters_per_room': max_monsters_per_room,
        'max_items_per_room': max_items_per_room,
        'colors': colors
    }

    return constants

*Note: window_title is new. Before, we were just passing the title of the window as a string, but we might as well define it as part of this dictionary.

Why the name “constants”? Python doesn’t have a way to declare a variable that never changes (Java has “final”, C# has “readonly”, etc.), so I wanted a name that conveys the fact that these variable’s shouldn’t change. The program could, theoretically alter them during the course of the game, but for now, we won’t do that. You can use another name if you prefer, like “game_variables” or something to that effect.

Let’s put this function to work in our engine.py file. Import the function first:

...
from input_handlers import handle_keys, handle_mouse
+from loader_functions.initialize_new_game import get_constants
from map_objects.game_map import GameMap
...

...
from input_handlers import handle_keys, handle_mouse
from loader_functions.initialize_new_game import get_constants
from map_objects.game_map import GameMap
...

Then, call it in the first line of main. Let’s also remove those same variables :

def main():
+   constants = get_constants()

-   screen_width = 80
-   screen_height = 50

-   bar_width = 20
-   panel_height = 7
-   panel_y = screen_height - panel_height

-   message_x = bar_width + 2
-   message_width = screen_width - bar_width - 2
-   message_height = panel_height - 1

-   map_width = 80
-   map_height = 43

-   room_max_size = 10
-   room_min_size = 6
-   max_rooms = 30

-   fov_algorithm = 0
-   fov_light_walls = True
-   fov_radius = 10

-   max_monsters_per_room = 3
-   max_items_per_room = 2

-   colors = {
-       'dark_wall': (0, 0, 100),
-       'dark_ground': (50, 50, 150),
-       'light_wall': (130, 110, 50),
-       'light_ground': (200, 180, 50)
-   }

def main():
    constants = get_constants()

    screen_width = 80
    screen_height = 50

    bar_width = 20
    panel_height = 7
    panel_y = screen_height - panel_height

    message_x = bar_width + 2
    message_width = screen_width - bar_width - 2
    message_height = panel_height - 1

    map_width = 80
    map_height = 43

    room_max_size = 10
    room_min_size = 6
    max_rooms = 30

    fov_algorithm = 0
    fov_light_walls = True
    fov_radius = 10

    max_monsters_per_room = 3
    max_items_per_room = 2

    colors = {
        'dark_wall': (0, 0, 100),
        'dark_ground': (50, 50, 150),
        'light_wall': (130, 110, 50),
        'light_ground': (200, 180, 50)
    }

Okay, so if you’re using an IDE (like PyCharm), then it’s probably going crazy right now. Obviously we can’t just remove that many variables and expect everything to be just fine. We have to modify all the times we used those “constant” variables directly, and replace then with a lookup to the constants dictionary.

   ...
   libtcod.console_set_custom_font('arial10x10.png', libtcod.FONT_TYPE_GREYSCALE | libtcod.FONT_LAYOUT_TCOD)

-   libtcod.console_init_root(screen_width, screen_height, 'libtcod tutorial revised', False)
+   libtcod.console_init_root(constants['screen_width'], constants['screen_height'], constants['window_title'], False)

-   con = libtcod.console_new(screen_width, screen_height)
-   panel = libtcod.console_new(screen_width, panel_height)
+   con = libtcod.console_new(constants['screen_width'], constants['screen_height'])
+   panel = libtcod.console_new(constants['screen_width'], constants['panel_height'])

-   game_map = GameMap(map_width, map_height)
-   game_map.make_map(max_rooms, room_min_size, room_max_size, map_width, map_height, player, entities,
-                     max_monsters_per_room, max_items_per_room)
+   game_map = GameMap(constants['map_width'], constants['map_height'])
+   game_map.make_map(constants['max_rooms'], constants['room_min_size'], constants['room_max_size'],
+                     constants['map_width'], constants['map_height'], player, entities,
+                     constants['max_monsters_per_room'], constants['max_items_per_room'])

   fov_recompute = True

   fov_map = initialize_fov(game_map)

-   message_log = MessageLog(message_x, message_width, message_height)
+   message_log = MessageLog(constants['message_x'], constants['message_width'], constants['message_height'])

   key = libtcod.Key()

    ...
    libtcod.console_set_custom_font('arial10x10.png', libtcod.FONT_TYPE_GREYSCALE | libtcod.FONT_LAYOUT_TCOD)

    libtcod.console_init_root(screen_width, screen_height, 'libtcod tutorial revised', False)
    libtcod.console_init_root(constants['screen_width'], constants['screen_height'], constants['window_title'], False)

    con = libtcod.console_new(screen_width, screen_height)
    panel = libtcod.console_new(screen_width, panel_height)
    con = libtcod.console_new(constants['screen_width'], constants['screen_height'])
    panel = libtcod.console_new(constants['screen_width'], constants['panel_height'])

    game_map = GameMap(map_width, map_height)
    game_map.make_map(max_rooms, room_min_size, room_max_size, map_width, map_height, player, entities,
                      max_monsters_per_room, max_items_per_room)
    game_map = GameMap(constants['map_width'], constants['map_height'])
    game_map.make_map(constants['max_rooms'], constants['room_min_size'], constants['room_max_size'],
                      constants['map_width'], constants['map_height'], player, entities,
                      constants['max_monsters_per_room'], constants['max_items_per_room'])

    fov_recompute = True

    fov_map = initialize_fov(game_map)

    message_log = MessageLog(message_x, message_width, message_height)
    message_log = MessageLog(constants['message_x'], constants['message_width'], constants['message_height'])

    key = libtcod.Key()

       ...
       if fov_recompute:
-           recompute_fov(fov_map, player.x, player.y, fov_radius, fov_light_walls, fov_algorithm)
+           recompute_fov(fov_map, player.x, player.y, constants['fov_radius'], constants['fov_light_walls'],
+                         constants['fov_algorithm'])

-       render_all(con, panel, entities, player, game_map, fov_map, fov_recompute, message_log, screen_width,
-                  screen_height, bar_width, panel_height, panel_y, mouse, colors, game_state)
+       render_all(con, panel, entities, player, game_map, fov_map, fov_recompute, message_log,
+                  constants['screen_width'], constants['screen_height'], constants['bar_width'],
+                  constants['panel_height'], constants['panel_y'], mouse, constants['colors'], game_state)

        ...
        if fov_recompute:
            recompute_fov(fov_map, player.x, player.y, fov_radius, fov_light_walls, fov_algorithm)
            recompute_fov(fov_map, player.x, player.y, constants['fov_radius'], constants['fov_light_walls'],
                          constants['fov_algorithm'])

        render_all(con, panel, entities, player, game_map, fov_map, fov_recompute, message_log, screen_width,
                   screen_height, bar_width, panel_height, panel_y, mouse, colors, game_state)
        render_all(con, panel, entities, player, game_map, fov_map, fov_recompute, message_log,
                   constants['screen_width'], constants['screen_height'], constants['bar_width'],
                   constants['panel_height'], constants['panel_y'], mouse, constants['colors'], game_state)

*Note: Why are we using the square bracket notation instead of the get() method? In most other spots, we’ve used the ‘get’ notation, but here I would argue it makes more sense to use the square brackets. Square brackets will outright crash our game if the variable isn’t found, which in this case, is probably what we’d want. The game can’t possibly proceed without these variables, so there’s no reason to try to continue the program without them.

That’s a lot of changes, but we’ve successfully removed the constant variables out of the main loop! Note that if you wanted to, you could shorten a lot of those function definitions by just passing the constants dictionary instead of passing only what the functions need. It doesn’t make a huge difference and is really a matter of preference. I’ll leave it as is in this tutorial, since changing the functions right now would be a ton of work.

What’s next? Another thing we could do is move the initialization of the player, entities list, and game’s map to a separate function. Put the following function in initialize_new_game.py:

def get_constants():
   ...

+def get_game_variables(constants):
+   fighter_component = Fighter(hp=30, defense=2, power=5)
+   inventory_component = Inventory(26)
+   player = Entity(0, 0, '@', libtcod.white, 'Player', blocks=True, render_order=RenderOrder.ACTOR,
+                   fighter=fighter_component, inventory=inventory_component)
+   entities = [player]
+
+   game_map = GameMap(constants['map_width'], constants['map_height'])
+   game_map.make_map(constants['max_rooms'], constants['room_min_size'], constants['room_max_size'],
+                     constants['map_width'], constants['map_height'], player, entities,
+                     constants['max_monsters_per_room'], constants['max_items_per_room'])
+
+   message_log = MessageLog(constants['message_x'], constants['message_width'], constants['message_height'])
+
+   game_state = GameStates.PLAYERS_TURN
+
+   return player, entities, game_map, message_log, game_state

def get_constants():
    ...

def get_game_variables(constants):
    fighter_component = Fighter(hp=30, defense=2, power=5)
    inventory_component = Inventory(26)
    player = Entity(0, 0, '@', libtcod.white, 'Player', blocks=True, render_order=RenderOrder.ACTOR,
                    fighter=fighter_component, inventory=inventory_component)
    entities = [player]

    game_map = GameMap(constants['map_width'], constants['map_height'])
    game_map.make_map(constants['max_rooms'], constants['room_min_size'], constants['room_max_size'],
                      constants['map_width'], constants['map_height'], player, entities,
                      constants['max_monsters_per_room'], constants['max_items_per_room'])

    message_log = MessageLog(constants['message_x'], constants['message_width'], constants['message_height'])

    game_state = GameStates.PLAYERS_TURN

    return player, entities, game_map, message_log, game_state

We’ll need to include a few imports in initialize_new_game.py for this:

import tcod as libtcod

+from components.fighter import Fighter
+from components.inventory import Inventory
+
+from entity import Entity
+
+from game_messages import MessageLog
+
+from game_states import GameStates
+
+from map_objects.game_map import GameMap
+
+from render_functions import RenderOrder


def get_constants():
   ...

import tcod as libtcod

from components.fighter import Fighter
from components.inventory import Inventory

from entity import Entity

from game_messages import MessageLog

from game_states import GameStates

from map_objects.game_map import GameMap

from render_functions import RenderOrder


def get_constants():
    ...

Nothing has changed about the way we’re initializing these variables. All we’re doing is putting it in one function, which we’ll call once in our main game loop. Let’s do that now. Start by importing the get_game_variables function:

...
from input_handlers import handle_keys, handle_mouse
-from loader_functions.initialize_new_game import get_constants
+from loader_functions.initialize_new_game import get_constants, get_game_variables
from map_objects.game_map import GameMap
...

...
from input_handlers import handle_keys, handle_mouse
from loader_functions.initialize_new_game import get_constants, get_game_variables
from map_objects.game_map import GameMap
...

Then modify the main function like this:

   ...
-   fighter_component = Fighter(hp=30, defense=2, power=5)
-   inventory_component = Inventory(26)
-   player = Entity(0, 0, '@', libtcod.white, 'Player', blocks=True, render_order=RenderOrder.ACTOR,
-                   fighter=fighter_component, inventory=inventory_component)
-   entities = [player]

   libtcod.console_set_custom_font('arial10x10.png', libtcod.FONT_TYPE_GREYSCALE | libtcod.FONT_LAYOUT_TCOD)

   libtcod.console_init_root(constants['screen_width'], constants['screen_height'], constants['window_title'], False)

   con = libtcod.console_new(constants['screen_width'], constants['screen_height'])
   panel = libtcod.console_new(constants['screen_width'], constants['panel_height'])

-   game_map = GameMap(constants['map_width'], constants['map_height'])
-   game_map.make_map(constants['max_rooms'], constants['room_min_size'], constants['room_max_size'],
-                     constants['map_width'], constants['map_height'], player, entities,
-                     constants['max_monsters_per_room'], constants['max_items_per_room'])

+   player, entities, game_map, message_log, game_state = get_game_variables(constants)

   fov_recompute = True

   fov_map = initialize_fov(game_map)

-   message_log = MessageLog(constants['message_x'], constants['message_width'], constants['message_height'])

   key = libtcod.Key()
   mouse = libtcod.Mouse()

-   game_state = GameStates.PLAYERS_TURN
   previous_game_state = game_state

   targeting_item = None
   ...

    ...
    fighter_component = Fighter(hp=30, defense=2, power=5)
    inventory_component = Inventory(26)
    player = Entity(0, 0, '@', libtcod.white, 'Player', blocks=True, render_order=RenderOrder.ACTOR,
                    fighter=fighter_component, inventory=inventory_component)
    entities = [player]

    libtcod.console_set_custom_font('arial10x10.png', libtcod.FONT_TYPE_GREYSCALE | libtcod.FONT_LAYOUT_TCOD)

    libtcod.console_init_root(constants['screen_width'], constants['screen_height'], constants['window_title'], False)

    con = libtcod.console_new(constants['screen_width'], constants['screen_height'])
    panel = libtcod.console_new(constants['screen_width'], constants['panel_height'])

    game_map = GameMap(constants['map_width'], constants['map_height'])
    game_map.make_map(constants['max_rooms'], constants['room_min_size'], constants['room_max_size'],
                      constants['map_width'], constants['map_height'], player, entities,
                      constants['max_monsters_per_room'], constants['max_items_per_room'])

    player, entities, game_map, message_log, game_state = get_game_variables(constants)

    fov_recompute = True

    fov_map = initialize_fov(game_map)

    message_log = MessageLog(constants['message_x'], constants['message_width'], constants['message_height'])

    key = libtcod.Key()
    mouse = libtcod.Mouse()

    game_state = GameStates.PLAYERS_TURN
    previous_game_state = game_state

    targeting_item = None
    ...

One interesting effect of removing these lines is that we don’t need all the imports we did before. Modify your import section at the top of engine.py to look like this:

import tcod as libtcod

-from components.fighter import Fighter
-from components.inventory import Inventory
from death_functions import kill_monster, kill_player
-from entity import Entity, get_blocking_entities_at_location
+from entity get_blocking_entities_at_location
from fov_functions import initialize_fov, recompute_fov
-from game_messages import Message, MessageLog
+from game_messages import Message
from game_states import GameStates
from input_handlers import handle_keys, handle_mouse
from loader_functions.initialize_new_game import get_constants, get_game_variables
-from map_objects.game_map import GameMap
-from render_functions import clear_all, render_all, RenderOrder
+from render_functions import clear_all, render_all

import tcod as libtcod

from components.fighter import Fighter
from components.inventory import Inventory
from death_functions import kill_monster, kill_player
from entity import Entity, get_blocking_entities_at_location
from fov_functions import initialize_fov, recompute_fov
from game_messages import Message, MessageLog
from game_states import GameStates
from input_handlers import handle_keys, handle_mouse
from loader_functions.initialize_new_game import get_constants, get_game_variables
from map_objects.game_map import GameMap
from render_functions import clear_all, render_all, RenderOrder

It’s time to think about how we’re going to save and load our game. In order for this to happen, we’ll need to save some (not necessarily all) of our data to some sort of persistent external location. In many applications, this would be a SQL or NoSQL database, but that’s probably overkill for our little project. Instead, we’ll just save to a data file.

So what exactly do we need to save? The key things are the entities list (including the player), the game’s map, the message log, and the game’s state. These are the same variables we got from the game’s initialization function too, so we’ll be able to start a new game or load an old one by just swapping our the respective functions. More on that later.

Unfortunately, plain JSON isn’t quite enough to save and load our data. Our objects are too complex to just save to straight JSON. There are a few solutions to this. The first would be to write serializers for our classes and objects ourselves, which isn’t a bad idea. But in the interest of keeping things simple for this tutorial, we’ll just use a library; specifically: shelve. This library allows you to save and load complex Python objects, without needing to write custom serializers.

Create a new file in loader_functions, called data_loaders.py. We’ll start by writing our save function.

import shelve


def save_game(player, entities, game_map, message_log, game_state):
    with shelve.open('savegame.dat', 'n') as data_file:
        data_file['player_index'] = entities.index(player)
        data_file['entities'] = entities
        data_file['game_map'] = game_map
        data_file['message_log'] = message_log
        data_file['game_state'] = game_state

Using shelve, we’re encoding the data into a dictionary which we’ll save to the file later. Note that we’re not actually saving the player, because the player is already part of the entities list. We just need the index in the list, so that we can load the player from that list later.

And that’s all we need to save the game! Without the shelve module, it would have taken far more effort to be able to save our game. Luckily, it also makes loading our game easy too; let’s implement that now. In the same file (data_loaders.py), create a new function called load_game. You’ll need to import GameMap in order for this to work.

+import os

import shelve


def save_game(player, entities, game_map, message_log, game_state):
   ...

+def load_game():
+   if not os.path.isfile('savegame.dat'):
+       raise FileNotFoundError
+
+   with shelve.open('savegame.dat', 'r') as data_file:
+       player_index = data_file['player_index']
+       entities = data_file['entities']
+       game_map = data_file['game_map']
+       message_log = data_file['message_log']
+       game_state = data_file['game_state']
+
+   player = entities[player_index]
+
+   return player, entities, game_map, message_log, game_state

import os

import shelve


def save_game(player, entities, game_map, message_log, game_state):
    ...

def load_game():
    if not os.path.isfile('savegame.dat'):
        raise FileNotFoundError

    with shelve.open('savegame.dat', 'r') as data_file:
        player_index = data_file['player_index']
        entities = data_file['entities']
        game_map = data_file['game_map']
        message_log = data_file['message_log']
        game_state = data_file['game_state']

    player = entities[player_index]

    return player, entities, game_map, message_log, game_state

This is just the reverse of the save function. We pull the data out of the data file, and return all the variables needed to the engine.

The functions for saving and loading are done, but now we need a way to use them. Before we do that, it’s probably a good time to think about how our game starts up in the first place. Right now, the game just starts, throwing the player straight into a new game. But that’s not how games typically work. Almost every game in existence has some sort of starting screen, which lets the player start a new game, load an existing one, exit, or maybe edit some options. Let’s implement something similar for ours; we should let the player start a new game, load an existing one, or quit.

We’ll need a new menu function to display our main menu. Open up menus.py and add the following function to it:

def inventory_menu(con, header, inventory, inventory_width, screen_width, screen_height):
   ...


+def main_menu(con, background_image, screen_width, screen_height):
+   libtcod.image_blit_2x(background_image, 0, 0, 0)
+
+   libtcod.console_set_default_foreground(0, libtcod.light_yellow)
+   libtcod.console_print_ex(0, int(screen_width / 2), int(screen_height / 2) - 4, libtcod.BKGND_NONE, libtcod.CENTER,
+                            'TOMBS OF THE ANCIENT KINGS')
+   libtcod.console_print_ex(0, int(screen_width / 2), int(screen_height - 2), libtcod.BKGND_NONE, libtcod.CENTER,
+                            'By (Your name here)')
+
+   menu(con, '', ['Play a new game', 'Continue last game', 'Quit'], 24, screen_width, screen_height)

def inventory_menu(con, header, inventory, inventory_width, screen_width, screen_height):
    ...


def main_menu(con, background_image, screen_width, screen_height):
    libtcod.image_blit_2x(background_image, 0, 0, 0)

    libtcod.console_set_default_foreground(0, libtcod.light_yellow)
    libtcod.console_print_ex(0, int(screen_width / 2), int(screen_height / 2) - 4, libtcod.BKGND_NONE, libtcod.CENTER,
                             'TOMBS OF THE ANCIENT KINGS')
    libtcod.console_print_ex(0, int(screen_width / 2), int(screen_height - 2), libtcod.BKGND_NONE, libtcod.CENTER,
                             'By (Your name here)')

    menu(con, '', ['Play a new game', 'Continue last game', 'Quit'], 24, screen_width, screen_height)

Our “main” function right now operates off the assumption that we’re going straight into the game. A better method of handling this would be to have the “main” function open the main menu, and, if the player chooses to either start a new game or continue an old one, the main game starts. We can move the logic of the main game to a separate function, which we’ll call play_game. This function will live in our engine.py file (it doesn’t have to, but it doesn’t make much sense to put it elsewhere right now).

*Note: I won’t bother with code highlighting here, there’s just too much to cover.

def play_game(player, entities, game_map, message_log, game_state, con, panel, constants):
    fov_recompute = True

    fov_map = initialize_fov(game_map)

    key = libtcod.Key()
    mouse = libtcod.Mouse()

    game_state = GameStates.PLAYERS_TURN
    previous_game_state = game_state

    targeting_item = None

    while not libtcod.console_is_window_closed():
        libtcod.sys_check_for_event(libtcod.EVENT_KEY_PRESS | libtcod.EVENT_MOUSE, key, mouse)

        if fov_recompute:
            recompute_fov(fov_map, player.x, player.y, constants['fov_radius'], constants['fov_light_walls'],
                          constants['fov_algorithm'])

        render_all(con, panel, entities, player, game_map, fov_map, fov_recompute, message_log,
                   constants['screen_width'], constants['screen_height'], constants['bar_width'],
                   constants['panel_height'], constants['panel_y'], mouse, constants['colors'], game_state)

        fov_recompute = False

        libtcod.console_flush()

        clear_all(con, entities)

        action = handle_keys(key, game_state)
        mouse_action = handle_mouse(mouse)

        move = action.get('move')
        pickup = action.get('pickup')
        show_inventory = action.get('show_inventory')
        drop_inventory = action.get('drop_inventory')
        inventory_index = action.get('inventory_index')
        exit = action.get('exit')
        fullscreen = action.get('fullscreen')

        left_click = mouse_action.get('left_click')
        right_click = mouse_action.get('right_click')

        player_turn_results = []

        if move and game_state == GameStates.PLAYERS_TURN:
            dx, dy = move
            destination_x = player.x + dx
            destination_y = player.y + dy

            if not game_map.is_blocked(destination_x, destination_y):
                target = get_blocking_entities_at_location(entities, destination_x, destination_y)

                if target:
                    attack_results = player.fighter.attack(target)
                    player_turn_results.extend(attack_results)
                else:
                    player.move(dx, dy)

                    fov_recompute = True

                game_state = GameStates.ENEMY_TURN

        elif pickup and game_state == GameStates.PLAYERS_TURN:
            for entity in entities:
                if entity.item and entity.x == player.x and entity.y == player.y:
                    pickup_results = player.inventory.add_item(entity)
                    player_turn_results.extend(pickup_results)

                    break
            else:
                message_log.add_message(Message('There is nothing here to pick up.', libtcod.yellow))

        if show_inventory:
            previous_game_state = game_state
            game_state = GameStates.SHOW_INVENTORY

        if drop_inventory:
            previous_game_state = game_state
            game_state = GameStates.DROP_INVENTORY

        if inventory_index is not None and previous_game_state != GameStates.PLAYER_DEAD and inventory_index < len(
                player.inventory.items):
            item = player.inventory.items[inventory_index]

            if game_state == GameStates.SHOW_INVENTORY:
                player_turn_results.extend(player.inventory.use(item, entities=entities, fov_map=fov_map))
            elif game_state == GameStates.DROP_INVENTORY:
                player_turn_results.extend(player.inventory.drop_item(item))

        if game_state == GameStates.TARGETING:
            if left_click:
                target_x, target_y = left_click

                item_use_results = player.inventory.use(targeting_item, entities=entities, fov_map=fov_map,
                                                        target_x=target_x, target_y=target_y)
                player_turn_results.extend(item_use_results)
            elif right_click:
                player_turn_results.append({'targeting_cancelled': True})

        if exit:
            if game_state in (GameStates.SHOW_INVENTORY, GameStates.DROP_INVENTORY):
                game_state = previous_game_state
            elif game_state == GameStates.TARGETING:
                player_turn_results.append({'targeting_cancelled': True})
            else:
                save_game(player, entities, game_map, message_log, game_state)

                return True

        if fullscreen:
            libtcod.console_set_fullscreen(not libtcod.console_is_fullscreen())

        for player_turn_result in player_turn_results:
            message = player_turn_result.get('message')
            dead_entity = player_turn_result.get('dead')
            item_added = player_turn_result.get('item_added')
            item_consumed = player_turn_result.get('consumed')
            item_dropped = player_turn_result.get('item_dropped')
            targeting = player_turn_result.get('targeting')
            targeting_cancelled = player_turn_result.get('targeting_cancelled')

            if message:
                message_log.add_message(message)

            if dead_entity:
                if dead_entity == player:
                    message, game_state = kill_player(dead_entity)
                else:
                    message = kill_monster(dead_entity)

                message_log.add_message(message)

            if item_added:
                entities.remove(item_added)

                game_state = GameStates.ENEMY_TURN

            if item_consumed:
                game_state = GameStates.ENEMY_TURN

            if item_dropped:
                entities.append(item_dropped)

                game_state = GameStates.ENEMY_TURN

            if targeting:
                previous_game_state = GameStates.PLAYERS_TURN
                game_state = GameStates.TARGETING

                targeting_item = targeting

                message_log.add_message(targeting_item.item.targeting_message)

            if targeting_cancelled:
                game_state = previous_game_state

                message_log.add_message(Message('Targeting cancelled'))

        if game_state == GameStates.ENEMY_TURN:
            for entity in entities:
                if entity.ai:
                    enemy_turn_results = entity.ai.take_turn(player, fov_map, game_map, entities)

                    for enemy_turn_result in enemy_turn_results:
                        message = enemy_turn_result.get('message')
                        dead_entity = enemy_turn_result.get('dead')

                        if message:
                            message_log.add_message(message)

                        if dead_entity:
                            if dead_entity == player:
                                message, game_state = kill_player(dead_entity)
                            else:
                                message = kill_monster(dead_entity)

                            message_log.add_message(message)

                            if game_state == GameStates.PLAYER_DEAD:
                                break

                    if game_state == GameStates.PLAYER_DEAD:
                        break
            else:
                game_state = GameStates.PLAYERS_TURN

This is the same as our game code from before, just put into a function. We’ll pass all the needed variables in our main function. If the player presses escape during the game, we’ll return to the main loop, which displays the main menu. The one thing that is different here is that we’re calling save_game before exiting the loop.

Now let’s change our main loop. It’ll display the main menu, and depending on the player’s choice, it will either start a new game, load an existing one, or exit the program.

def main():
    constants = get_constants()

    libtcod.console_set_custom_font('arial10x10.png', libtcod.FONT_TYPE_GREYSCALE | libtcod.FONT_LAYOUT_TCOD)

    libtcod.console_init_root(constants['screen_width'], constants['screen_height'], constants['window_title'], False)

    con = libtcod.console_new(constants['screen_width'], constants['screen_height'])
    panel = libtcod.console_new(constants['screen_width'], constants['panel_height'])

    player = None
    entities = []
    game_map = None
    message_log = None
    game_state = None

    show_main_menu = True
    show_load_error_message = False

    main_menu_background_image = libtcod.image_load('menu_background.png')

    key = libtcod.Key()
    mouse = libtcod.Mouse()

    while not libtcod.console_is_window_closed():
        libtcod.sys_check_for_event(libtcod.EVENT_KEY_PRESS | libtcod.EVENT_MOUSE, key, mouse)

        if show_main_menu:
            main_menu(con, main_menu_background_image, constants['screen_width'],
                      constants['screen_height'])

            if show_load_error_message:
                message_box(con, 'No save game to load', 50, constants['screen_width'], constants['screen_height'])

            libtcod.console_flush()

            action = handle_main_menu(key)

            new_game = action.get('new_game')
            load_saved_game = action.get('load_game')
            exit_game = action.get('exit')

            if show_load_error_message and (new_game or load_saved_game or exit_game):
                show_load_error_message = False
            elif new_game:
                player, entities, game_map, message_log, game_state = get_game_variables(constants)
                game_state = GameStates.PLAYERS_TURN

                show_main_menu = False
            elif load_saved_game:
                try:
                    player, entities, game_map, message_log, game_state = load_game()
                    show_main_menu = False
                except FileNotFoundError:
                    show_load_error_message = True
            elif exit_game:
                break

        else:
            libtcod.console_clear(con)
            play_game(player, entities, game_map, message_log, game_state, con, panel, constants)

            show_main_menu = True

We’re loading a background image with image_load to display in our main menu. The sample image used for this tutorial can be found here. Download it and put in in your project’s directory.

Other than that, a lot of this should look familiar. We’re displaying the main menu with three options, and accepting keyboard input to determine which option to go with. If the user starts a new game, we use our get_game_variables function from earlier, and if an old game is being loaded, we use the load_game function. Either way, we get the same variables. Assuming one of those options was chosen, we pass the variables off to the play_game function, and the game proceeds as it has been until now.

We haven’t implemented the message_box or handle_main_menu functions yet, so let’s do so now. We’ll start with message_box and we’ll put it in menus.py, at the bottom of the file:

+def message_box(con, header, width, screen_width, screen_height):
+   menu(con, header, [], width, screen_width, screen_height)

def message_box(con, header, width, screen_width, screen_height):
    menu(con, header, [], width, screen_width, screen_height)

Pretty straightforward. The message box is just an empty menu, basically.

Now on to handle_main_menu, which goes in input_handlers.py:

def handle_inventory_keys(key):
   ...

+def handle_main_menu(key):
+   key_char = chr(key.c)
+
+   if key_char == 'a':
+       return {'new_game': True}
+   elif key_char == 'b':
+       return {'load_game': True}
+   elif key_char == 'c' or  key.vk == libtcod.KEY_ESCAPE:
+       return {'exit': True}
+
+   return {}


def handle_mouse(mouse):
   ...

def handle_inventory_keys(key):
    ...

def handle_main_menu(key):
    key_char = chr(key.c)

    if key_char == 'a':
        return {'new_game': True}
    elif key_char == 'b':
        return {'load_game': True}
    elif key_char == 'c' or  key.vk == libtcod.KEY_ESCAPE:
        return {'exit': True}

    return {}


def handle_mouse(mouse):
    ...

Nothing too complicated here: Our main menu will have 3 options, so just return the result of which option was selected. Note that the ‘Quit’ option can be done through the ‘c’ key or ‘Escape’.

Remember to import these new functions into engine.py:

import tcod as libtcod

from death_functions import kill_monster, kill_player
from entity import get_blocking_entities_at_location
from fov_functions import initialize_fov, recompute_fov
from game_messages import Message
from game_states import GameStates
-from input_handlers import handle_keys, handle_mouse
+from input_handlers import handle_keys, handle_mouse, handle_main_menu
from loader_functions.initialize_new_game import get_constants, get_game_variables
+from loader_functions.data_loaders import load_game, save_game
+from menus import main_menu, message_box
from render_functions import clear_all, render_all
...

import tcod as libtcod

from death_functions import kill_monster, kill_player
from entity import get_blocking_entities_at_location
from fov_functions import initialize_fov, recompute_fov
from game_messages import Message
from game_states import GameStates
from input_handlers import handle_keys, handle_mouse, handle_main_menu
from loader_functions.initialize_new_game import get_constants, get_game_variables
from loader_functions.data_loaders import load_game, save_game
from menus import main_menu, message_box
from render_functions import clear_all, render_all
...

That’s all for this chapter. The gameplay itself hasn’t changed, but saving and loading is no small feat. Be proud!

If you want to see the code so far in its entirety, click here.

Click here to move on to the next part of this tutorial.