3. Player Characters

In the previous lesson about rules and dice rolling we made some assumptions about the “Player Character” entity:

• It should store Abilities on itself as character.strength, character.constitution etc.

• It should have a .heal(amount) method.

So we have some guidelines of how it should look! A Character is a database entity with values that should be able to be changed over time. It makes sense to base it off Evennia’s DefaultCharacter Typeclass. The Character class is like a ‘character sheet’ in a tabletop RPG, it will hold everything relevant to that PC.

3.1. Inheritance structure

Player Characters (PCs) are not the only “living” things in our world. We also have NPCs (like shopkeepers and other friendlies) as well as monsters (mobs) that can attack us.

In code, there are a few ways we could structure this. If NPCs/monsters were just special cases of PCs, we could use a class inheritance like this:

from evennia import DefaultCharacter 

class EvAdventureCharacter(DefaultCharacter): 
    # stuff 
    
class EvAdventureNPC(EvAdventureCharacter):
    # more stuff 
    
class EvAdventureMob(EvAdventureNPC): 
    # more stuff 

All code we put on the Character class would now be inherited to NPC and Mob automatically.

However, in Knave, NPCs and particularly monsters are not using the same rules as PCs - they are simplified to use a Hit-Die (HD) concept. So while still character-like, NPCs should be separate from PCs like this:

from evennia import DefaultCharacter 

class EvAdventureCharacter(DefaultCharacter): 
    # stuff 

class EvAdventureNPC(DefaultCharacter):
    # separate stuff 
    
class EvAdventureMob(EvadventureNPC):
    # more separate stuff

Nevertheless, there are some things that should be common for all ‘living things’:

• All can take damage.

• All can die.

• All can heal

• All can hold and lose coins

• All can loot their fallen foes.

• All can get looted when defeated.

We don’t want to code this separately for every class but we no longer have a common parent class to put it on. So instead we’ll use the concept of a mixin class:

from evennia import DefaultCharacter 

class LivingMixin:
    # stuff common for all living things

class EvAdventureCharacter(LivingMixin, DefaultCharacter): 
    # stuff 

class EvAdventureNPC(LivingMixin, DefaultCharacter):
    # stuff 
    
class EvAdventureMob(LivingMixin, EvadventureNPC):
    # more stuff

In evennia/contrib/tutorials/evadventure/characters.py is an example of a character class structure.

Above, the LivingMixin class cannot work on its own - it just ‘patches’ the other classes with some extra functionality all living things should be able to do. This is an example of multiple inheritance. It’s useful to know about, but one should not over-do multiple inheritance since it can also get confusing to follow the code.

3.2. Living mixin class

Create a new module mygame/evadventure/characters.py

Let’s get some useful common methods all living things should have in our game.

# in mygame/evadventure/characters.py 

from .rules import dice 

class LivingMixin:

    # makes it easy for mobs to know to attack PCs
    is_pc = False  

    def heal(self, hp): 
        """ 
        Heal hp amount of health, not allowing to exceed our max hp
         
        """ 
        damage = self.hp_max - self.hp 
        healed = min(damage, hp) 
        self.hp += healed 
        
        self.msg("You heal for {healed} HP.") 
        
    def at_pay(self, amount):
        """When paying coins, make sure to never detract more than we have"""
        amount = min(amount, self.coins)
        self.coins -= amount
        return amount
        
    def at_damage(self, damage, attacker=None):
        """Called when attacked and taking damage."""
        self.hp -= damage  
        
    def at_defeat(self): 
        """Called when defeated. By default this means death."""
        self.at_death()
        
    def at_death(self):
        """Called when this thing dies."""
        # this will mean different things for different living things
        pass 
        
    def at_do_loot(self, looted):
        """Called when looting another entity""" 
        looted.at_looted(self)
        
    def at_looted(self, looter):
        """Called when looted by another entity""" 
        
        # default to stealing some coins 
        max_steal = dice.roll("1d10") 
        stolen = self.at_pay(max_steal)
        looter.coins += stolen

Most of these are empty since they will behave differently for characters and npcs. But having them in the mixin means we can expect these methods to be available for all living things.

3.3. Character class

We will now start making the basic Character class, based on what we need from Knave.

# in mygame/evadventure/characters.py

from evennia import DefaultCharacter, AttributeProperty
from .rules import dice 

class LivingMixin:
    # ... 


class EvAdventureCharacter(LivingMixin, DefaultCharacter):
    """ 
    A character to use for EvAdventure. 
    """
    is_pc = True 

    strength = AttributeProperty(1) 
    dexterity = AttributeProperty(1)
    constitution = AttributeProperty(1)
    intelligence = AttributeProperty(1)
    wisdom = AttributeProperty(1)
    charisma = AttributeProperty(1)
    
    hp = AttributeProperty(8) 
    hp_max = AttributeProperty(8)
    
    level = AttributeProperty(1)
    xp = AttributeProperty(0)
    coins = AttributeProperty(0)

    def at_defeat(self):
        """Characters roll on the death table"""
        if self.location.allow_death:
            # this allow rooms to have non-lethal battles
            dice.roll_death(self)
        else:
            self.location.msg_contents(
                "$You() $conj(collapse) in a heap, alive but beaten.",
                from_obj=self)
            self.heal(self.hp_max)
            
    def at_death(self):
        """We rolled 'dead' on the death table."""
        self.location.msg_contents(
            "$You() collapse in a heap, embraced by death.",
            from_obj=self) 
        # TODO - go back into chargen to make a new character!            

We make an assumption about our rooms here - that they have a property .allow_death. We need to make a note to actually add such a property to rooms later!

In our Character class we implement all attributes we want to simulate from the Knave ruleset. The AttributeProperty is one way to add an Attribute in a field-like way; these will be accessible on every character in several ways:

• As character.strength

• As character.db.strength

• As character.attributes.get("strength")

See Attributes for seeing how Attributes work.

Unlike in base Knave, we store coins as a separate Attribute rather than as items in the inventory, this makes it easier to handle barter and trading later.

We implement the Player Character versions of at_defeat and at_death. We also make use of .heal() from the LivingMixin class.

3.3.1. Funcparser inlines

This piece of code is worth some more explanation:

self.location.msg_contents(
    "$You() $conj(collapse) in a heap, alive but beaten.",
    from_obj=self)

Remember that self is the Character instance here. So self.location.msg_contents means “send a message to everything inside my current location”. In other words, send a message to everyone in the same place as the character.

The $You() $conj(collapse) are FuncParser inlines. These are functions that execute in the string. The resulting string may look different for different audiences. The $You() inline function will use from_obj to figure out who ‘you’ are and either show your name or ‘You’. The $conj() (verb conjugator) will tweak the (English) verb to match.

• You will see: "You collapse in a heap, alive but beaten."

• Others in the room will see: "Thomas collapses in a heap, alive but beaten."

Note how $conj() chose collapse/collapses to make the sentences grammatically correct.

3.3.2. Backtracking

We make our first use of the rules.dice roller to roll on the death table! As you may recall, in the previous lesson, we didn’t know just what to do when rolling ‘dead’ on this table. Now we know - we should be calling at_death on the character. So let’s add that where we had TODOs before:

# mygame/evadventure/rules.py 

class EvAdventureRollEngine:
    
    # ... 

    def roll_death(self, character): 
        ability_name = self.roll_random_table("1d8", death_table)

        if ability_name == "dead":
            # kill the character!
            character.at_death()  # <------ TODO no more
        else: 
            # ... 
                        
            if current_ability < -10: 
                # kill the character!
                character.at_death()  # <------- TODO no more
            else:
                # ... 

3.4. Connecting the Character with Evennia

You can easily make yourself an EvAdventureCharacter in-game by using the type command:

type self = evadventure.characters.EvAdventureCharacter

You can now do examine self to check your type updated.

If you want all new Characters to be of this type you need to tell Evennia about it. Evennia uses a global setting BASE_CHARACTER_TYPECLASS to know which typeclass to use when creating Characters (when logging in, for example). This defaults to typeclasses.characters.Character (that is, the Character class in mygame/typeclasses/characters.py).

There are thus two ways to weave your new Character class into Evennia:

1. Change mygame/server/conf/settings.py and add BASE_CHARACTER_CLASS = "evadventure.characters.EvAdventureCharacter".

2. Or, change typeclasses.characters.Character to inherit from EvAdventureCharacter.

You must always reload the server for changes like this to take effect.

Important

In this tutorial we are making all changes in a folder mygame/evadventure/. This means we can isolate our code but means we need to do some extra steps to tie the character (and other objects) into Evennia. For your own game it would be just fine to start editing mygame/typeclasses/characters.py directly instead.

3.5. Unit Testing

Create a new module mygame/evadventure/tests/test_characters.py

For testing, we just need to create a new EvAdventure character and check that calling the methods on it doesn’t error out.

# mygame/evadventure/tests/test_characters.py 

from evennia.utils import create
from evennia.utils.test_resources import BaseEvenniaTest 

from ..characters import EvAdventureCharacter 

class TestCharacters(BaseEvenniaTest):
    def setUp(self):
        super().setUp()
        self.character = create.create_object(EvAdventureCharacter, key="testchar")

    def test_heal(self):
        self.character.hp = 0 
        self.character.hp_max = 8 
        
        self.character.heal(1)
        self.assertEqual(self.character.hp, 1)
        # make sure we can't heal more than max
        self.character.heal(100)
        self.assertEqual(self.character.hp, 8)
        
    def test_at_pay(self):
        self.character.coins = 100 
        
        result = self.character.at_pay(60)
        self.assertEqual(result, 60) 
        self.assertEqual(self.character.coins, 40)
        
        # can't get more coins than we have 
        result = self.character.at_pay(100)
        self.assertEqual(result, 40)
        self.assertEqual(self.character.coins, 0)
        
    # tests for other methods ... 

If you followed the previous lessons, these tests should look familiar. Consider adding tests for other methods as practice. Refer to previous lessons for details.

For running the tests you do:

 evennia test --settings settings.py .evadventure.tests.test_character

3.6. About races and classes

Knave doesn’t have any D&D-style classes (like Thief, Fighter etc). It also does not bother with races (like dwarves, elves etc). This makes the tutorial shorter, but you may ask yourself how you’d add these functions.

In the framework we have sketched out for Knave, it would be simple - you’d add your race/class as an Attribute on your Character:

# mygame/evadventure/characters.py

from evennia import DefaultCharacter, AttributeProperty
# ... 

class EvAdventureCharacter(LivingMixin, DefaultCharacter):
    
    # ... 

    charclass = AttributeProperty("Fighter")
    charrace = AttributeProperty("Human")

We use charclass rather than class here, because class is a reserved Python keyword. Naming race as charrace thus matches in style.

We’d then need to expand our rules module (and later character generation to check and include what these classes mean.

3.7. Summary

With the EvAdventureCharacter class in place, we have a better understanding of how our PCs will look like under Knave.

For now, we only have bits and pieces and haven’t been testing this code in-game. But if you want you can swap yourself into EvAdventureCharacter right now. Log into your game and run the command

type self = evadventure.characters.EvAdventureCharacter 

If all went well, ex self will now show your typeclass as being EvAdventureCharacter. Check out your strength with

py self.strength = 3

Important

When doing ex self you will not see all your Abilities listed yet. That’s because Attributes added with AttributeProperty are not available until they have been accessed at least once. So once you set (or look at) .strength above, strength will show in examine from then on.