evennia.contrib.rpg.traits.traits¶

Traits

Whitenoise 2014, Ainneve contributors, Griatch 2020

A Trait represents a modifiable property on (usually) a Character. They can be used to represent everything from attributes (str, agi etc) to skills (hunting 10, swords 14 etc) and dynamically changing things like HP, XP etc.

Traits use Evennia Attributes under the hood, making them persistent (they survive a server reload/reboot).

Installation¶

Traits are always added to a typeclass, such as the Character class.

There are two ways to set up Traits on a typeclass. The first sets up the TraitHandler as a property .traits on your class and you then access traits as e.g. .traits.strength. The other alternative uses a TraitProperty, which makes the trait available directly as e.g. .strength. This solution also uses the TraitHandler, but you don’t need to define it explicitly. You can combine both styles if you like.

Traits with TraitHandler¶

Here’s an example for adding the TraitHandler to the Character class:

# mygame/typeclasses/objects.py

from evennia import DefaultCharacter
from evennia.utils import lazy_property
from evennia.contrib.rpg.traits import TraitHandler

# ...

class Character(DefaultCharacter):
    ...
    @lazy_property
    def traits(self):
        # this adds the handler as .traits
        return TraitHandler(self)


    def at_object_creation(self):
        # (or wherever you want)
        self.traits.add("str", "Strength", trait_type="static", base=10, mod=2, mult=2.0)
        self.traits.add("hp", "Health", trait_type="gauge", min=0, max=100)
        self.traits.add("hunting", "Hunting Skill", trait_type="counter",
                        base=10, mod=1, min=0, max=100)

When adding the trait, you supply the name of the property (hunting) along with a more human-friendly name (“Hunting Skill”). The latter will show if you print the trait etc. The trait_type is important, this specifies which type of trait this is (see below).

TraitProperties¶

Using TraitProperties makes the trait available directly on the class, much like Django model fields. The drawback is that you must make sure that the name of your Traits don’t collide with any other properties/methods on your class.

# mygame/typeclasses/objects.py

from evennia import DefaultObject
from evennia.utils import lazy_property
from evennia.contrib.rpg.traits import TraitProperty

# ...

class Object(DefaultObject):
    ...
    strength = TraitProperty("Strength", trait_type="static", base=10, mod=2, mult=1.5)
    health = TraitProperty("Health", trait_type="gauge", min=0, base=100, mod=2)
    hunting = TraitProperty("Hunting Skill", trait_type="counter", base=10, mod=1, mult=2.0, min=0, max=100)

> Note that the property-name will become the name of the trait and you don’t supply trait_key > separately.

> The .traits TraitHandler will still be created (it’s used under the > hood. But it will only be created when the TraitProperty has been accessed at least once, > so be careful if mixing the two styles. If you want to make sure .traits is always available, > add the TraitHandler manually like shown earlier - the TraitProperty will by default use > the same handler (.traits).

Using traits¶

A trait is added to the traithandler (if you use TraitProperty the handler is just created under the hood) after which one can access it as a property on the handler (similarly to how you can do .db.attrname for Attributes in Evennia).

All traits have a _read-only_ field .value. This is only used to read out results, you never manipulate it directly (if you try, it will just remain unchanged). The .value is calculated based on combining fields, like .base and .mod - which fields are available and how they relate to each other depends on the trait type.

> obj.traits.strength.value
18                                  # (base + mod) * mult

> obj.traits.strength.base += 6
obj.traits.strength.value
27

> obj.traits.hp.value
102                                 # (base + mod) * mult

> obj.traits.hp.base -= 200
> obj.traits.hp.value
0                                   # min of 0

> obj.traits.hp.reset()
> obj.traits.hp.value
100

# you can also access properties like a dict
> obj.traits.hp["value"]
100

# you can store arbitrary data persistently for easy reference
> obj.traits.hp.effect = "poisoned!"
> obj.traits.hp.effect
"poisoned!"

# with TraitProperties:

> obj.hunting.value
22

> obj.strength.value += 5
> obj.strength.value
32

Trait types¶

All default traits have a read-only .value property that shows the relevant or ‘current’ value of the trait. Exactly what this means depends on the type of trait.

Traits can also be combined to do arithmetic with their .value, if both have a compatible type.

> trait1 + trait2
54

> trait1.value
3

> trait1 + 2
> trait1.value
5

Two numerical traits can also be compared (bigger-than etc), which is useful in all sorts of rule-resolution.

if trait1 > trait2:
    # do stuff

Static trait¶

value = (base + mod) * mult

The static trait has a base value and an optional mod-ifier and ‘mult’-iplier. The modifier defaults to 0, and the multiplier to 1.0, for no change in value. A typical use of a static trait would be a Strength stat or Skill value. That is, somethingthat varies slowly or not at all, and which may be modified in-place.

> obj.traits.add("str", "Strength", trait_type="static", base=10, mod=2)
> obj.traits.mytrait.value
12   # base + mod

> obj.traits.mytrait.base += 2
> obj.traits.mytrait.mod += 1
> obj.traits.mytrait.value
15

> obj.traits.mytrait.mod = 0
> obj.traits.mytrait.mult = 2.0
> obj.traits.mytrait.value
20

Counter¶

min/unset     base    base+mod                       max/unset
|--------------|--------|---------X--------X------------|
                              current    value
                                         = (current
                                         + mod)
                                         * mult

A counter describes a value that can move from a base. The .current property is the thing usually modified. It starts at the .base. One can also add a modifier, which is added to both the base and to current. ‘.value’ is then formed by multiplying by the multiplier, which defaults to 1.0 for no change. The min/max of the range are optional, a boundary set to None will remove it. A suggested use for a Counter Trait would be to track skill values.

> obj.traits.add("hunting", "Hunting Skill", trait_type="counter",
                   base=10, mod=1, mult=1.0, min=0, max=100)
> obj.traits.hunting.value
11  # current starts at base + mod

> obj.traits.hunting.current += 10
> obj.traits.hunting.value
21

# reset back to base+mod by deleting current
> del obj.traits.hunting.current
> obj.traits.hunting.value
11

> obj.traits.hunting.max = None  # removing upper bound
> obj.traits.hunting.mult = 100.0
1100

# for TraitProperties, pass the args/kwargs of traits.add() to the
# TraitProperty constructor instead.

Counters have some extra properties:

.descs¶

The descs property is a dict {upper_bound:text_description}. This allows for easily storing a more human-friendly description of the current value in the interval. Here is an example for skill values between 0 and 10:

{0: "unskilled", 1: "neophyte", 5: "trained", 7: "expert", 9: "master"}

The keys must be supplied from smallest to largest. Any values below the lowest and above the highest description will be considered to be included in the closest description slot. By calling .desc() on the Counter, you will get the text matching the current value.

# (could also have passed descs= to traits.add())
> obj.traits.hunting.descs = {
    0: "unskilled", 10: "neophyte", 50: "trained", 70: "expert", 90: "master"}
> obj.traits.hunting.value
11

> obj.traits.hunting.desc()
"neophyte"
> obj.traits.hunting.current += 60
> obj.traits.hunting.value
71

> obj.traits.hunting.desc()
"expert"

.rate¶

The rate property defaults to 0. If set to a value different from 0, it allows the trait to change value dynamically. This could be used for example for an attribute that was temporarily lowered but will gradually (or abruptly) recover after a certain time. The rate is given as change of the current .value per-second, and this will still be restrained by min/max boundaries, if those are set.

It is also possible to set a .ratetarget, for the auto-change to stop at (rather than at the min/max boundaries). This allows the value to return to a previous value.

> obj.traits.hunting.value
71

> obj.traits.hunting.ratetarget = 71
# debuff hunting for some reason
> obj.traits.hunting.current -= 30
> obj.traits.hunting.value
41

> obj.traits.hunting.rate = 1  # 1/s increase
# Waiting 5s
> obj.traits.hunting.value
46

# Waiting 8s
> obj.traits.hunting.value
54

# Waiting 100s
> obj.traits.hunting.value
71    # we have stopped at the ratetarget

> obj.traits.hunting.rate = 0  # disable auto-change

Note that when retrieving the current, the result will always be of the same type as the .base even rate is a non-integer value. So if base is an int (default)**, the current value will also be rounded the closest full integer. If you want to see the exact current value, set base to a float - you will then need to use round() yourself on the result if you want integers.

.percent()¶

If both min and max are defined, the .percent() method of the trait will return the value as a percentage.

> obj.traits.hunting.percent()
"71.0%"

> obj.traits.hunting.percent(formatting=None)
71.0

Gauge¶

This emulates a [fuel-] gauge that empties from a base+mod value.

min/0                                            max=base+mod
 |-----------------------X---------------------------|
                       value
                      = current

The .current value will start from a full gauge. The .max property is read-only and is set by .base + .mod. So contrary to a Counter, the .mod modifier only applies to the max value of the gauge and not the current value. The minimum bound defaults to 0 if not set explicitly.

This trait is useful for showing commonly depletable resources like health, stamina and the like.

> obj.traits.add("hp", "Health", trait_type="gauge", base=100)
> obj.traits.hp.value  # (or .current)
100

> obj.traits.hp.mod = 10
> obj.traits.hp.value
110

> obj.traits.hp.current -= 30
> obj.traits.hp.value
80

The Gauge trait is subclass of the Counter, so you have access to the same methods and properties where they make sense. So gauges can also have a .descs dict to describe the intervals in text, and can use .percent() to get how filled it is as a percentage etc.

The .rate is particularly relevant for gauges - useful for everything from poison slowly draining your health, to resting gradually increasing it.

Trait¶

A single value of any type.

This is the ‘base’ Trait, meant to inherit from if you want to invent trait-types from scratch (most of the time you’ll probably inherit from some of the more advanced trait-type classes though).

Unlike other Trait-types, the single .value property of the base Trait can be editied. The value can hold any data that can be stored in an Attribute. If it’s an integer/float you can do arithmetic with it, but otherwise this acts just like a glorified Attribute.

> obj.traits.add("mytrait", "My Trait", trait_type="trait", value=30)
> obj.traits.mytrait.value
30

> obj.traits.mytrait.value = "stringvalue"
> obj.traits.mytrait.value
"stringvalue"

Expanding with your own Traits¶

A Trait is a class inhering from evennia.contrib.rpg.traits.Trait (or from one of the existing Trait classes).

# in a file, say, 'mygame/world/traits.py'

from evennia.contrib.rpg.traits import StaticTrait

class RageTrait(StaticTrait):

    trait_type = "rage"
    default_keys = {
        "rage": 0
    }

    def berserk(self):
        self.mod = 100

    def sedate(self):
        self.mod = 0

Above is an example custom-trait-class “rage” that stores a property “rage” on itself, with a default value of 0. This has all the functionality of a Trait - for example, if you do del on the rage property, it will be set back to its default (0). Above we also added some helper methods.

To add your custom RageTrait to Evennia, add the following to your settings file (assuming your class is in mygame/world/traits.py):

TRAIT_CLASS_PATHS = ["world.traits.RageTrait"]

Reload the server and you should now be able to use your trait:

> obj.traits.add("mood", "A dark mood", rage=30, trait_type='rage')
> obj.traits.mood.rage
30

# as TraitProperty

class Character(DefaultCharacter):
    rage = TraitProperty("A dark mood", rage=30, trait_type='rage')

exception evennia.contrib.rpg.traits.traits.TraitException(msg)[source]¶

Bases: RuntimeError

Base exception class raised by Trait objects.

Parameters: msg (str) – informative error message

__init__(msg)[source]¶: Initialize self. See help(type(self)) for accurate signature.

class evennia.contrib.rpg.traits.traits.MandatoryTraitKey[source]¶

Bases: object

This represents a required key that must be supplied when a Trait is initialized. It’s used by Trait classes when defining their required keys.

class evennia.contrib.rpg.traits.traits.TraitHandler(obj, db_attribute_key='traits', db_attribute_category='traits')[source]¶

Bases: object

Factory class that instantiates Trait objects. Must be assigned as a property on the class, usually with lazy_property.

Example:

class Object(DefaultObject):
    ...
    @lazy_property
    def traits(self):
        # this adds the handler as .traits
        return TraitHandler(self)

__init__(obj, db_attribute_key='traits', db_attribute_category='traits')[source]¶

Initialize the handler and set up its internal Attribute-based storage.

Parameters

obj (Object) – Parent Object typeclass for this TraitHandler
db_attribute_key (str) – Name of the DB attribute for trait data storage.
db_attribute_category (str) – Name of DB attribute’s category to trait data storage.

all()[source]¶

Get all trait keys in this handler.

Returns: list – All Trait keys.

get(trait_key)[source]¶

Parameters: trait_key (str) – key from the traits dict containing config data.
Returns: (Trait or None) – named Trait class or None if trait key is not found in traits collection.

add(trait_key, name=None, trait_type='static', force=True, **trait_properties)[source]¶

Create a new Trait and add it to the handler.

Parameters

trait_key (str) – This is the name of the property that will be made available on this handler (example ‘hp’).
name (str, optional) – Name of the Trait, like “Health”. If not given, will use trait_key starting with a capital letter.
trait_type (str, optional) – One of ‘static’, ‘counter’ or ‘gauge’.
force (bool) – If set, create a new Trait even if a Trait with the same trait_key already exists.
trait_properties (dict) – These will all be use to initialize the new trait. See the properties class variable on each Trait class to see which are required.

Raises

TraitException – If specifying invalid values for the given Trait, the trait_type is not recognized, or an existing trait already exists (and force is unset).

remove(trait_key)[source]¶

Remove a Trait from the handler’s parent object.

Parameters: trait_key (str) – The name of the trait to remove.

clear()[source]¶: Remove all Traits from the handler’s parent object.

class evennia.contrib.rpg.traits.traits.TraitProperty(name=None, trait_type='static', force=True, **trait_properties)[source]¶

Bases: object

Optional extra: Allows for applying traits as individual properties directly on the parent class instead for properties on the .traits handler. So with this you could access data e.g. as character.hp.value instead of character.traits.hp.value. This still uses the traitshandler under the hood.

Example:

from evennia.utils import lazy_property
from evennia.contrib.rpg.traits import TraitProperty

class Character(DefaultCharacter):

    strength = TraitProperty(name="STR", trait_type="static", base=10, mod=2)
    hunting = TraitProperty("Hunting Skill", trait_type="counter",
                            base=10, mod=1, max=100)
    health = TraitProperty(trait_type="gauge", min=0, base=100)

__init__(name=None, trait_type='static', force=True, **trait_properties)[source]¶

Initialize a TraitField. Mimics TraitHandler.add input except no trait_key.

Parameters

name (str, optional) – Name of the Trait, like “Health”. If not given, will use trait_key starting with a capital letter.
trait_type (str, optional) – One of ‘static’, ‘counter’ or ‘gauge’.
force (bool) – If set, create a new Trait even if a Trait with the same trait_key already exists.

Kwargs:

traithandler_name (str): If given, this is used as the name of the TraitHandler created: behind the scenes. If not set, this will be a property traits on the class.
any: All other trait_properties are the same as for adding a new trait of the given type: using the normal TraitHandler.

class evennia.contrib.rpg.traits.traits.Trait(trait_data)[source]¶

Bases: object

Represents an object or Character trait. This simple base is just storing anything in it’s ‘value’ property, so it’s pretty much just a different wrapper to an Attribute. It does no type-checking of what is stored.

Note

See module docstring for configuration details.

value

trait_type = 'trait'¶

default_keys = {'value': None}¶

allow_extra_properties = True¶

__init__(trait_data)[source]¶

This both initializes and validates the Trait on creation. It must raise exception if validation fails. The TraitHandler will call this when the trait is furst added, to make sure it validates before storing.

Parameters: trait_data (any) – Any pickle-able values to store with this trait. This must contain any cls.default_keys that do not have a default value in cls.data_default_values. Any extra kwargs will be made available as extra properties on the Trait, assuming the class variable allow_extra_properties is set.
Raises: TraitException – If input-validation failed.

static validate_input(cls, trait_data)[source]¶

Validate input

Parameters

trait_data (dict or _SaverDict) – Data to be used for initialization of this trait.

Returns

dict –

Validated data, possibly complemented with default: values from default_keys.

Raises

TraitException – If finding unset keys without a default.

property name¶: Display name for the trait.

property key¶: Display name for the trait.

property value¶: Store a value

class evennia.contrib.rpg.traits.traits.StaticTrait(trait_data)[source]¶

Bases: evennia.contrib.rpg.traits.traits.Trait

Static Trait. This is a single value with a modifier, multiplier, and no concept of a ‘current’ value or min/max etc.

value = (base + mod) * mult

trait_type = 'static'¶

default_keys = {'base': 0, 'mod': 0, 'mult': 1.0}¶

property base¶

property mod¶: The trait’s modifier.

property mult¶: The trait’s multiplier.

property value¶: The value of the Trait.

class evennia.contrib.rpg.traits.traits.CounterTrait(trait_data)[source]¶

Bases: evennia.contrib.rpg.traits.traits.Trait

Counter Trait.

This includes modifications and min/max limits as well as the notion of a current value. The value can also be reset to the base value.

min/unset base (base+mod)*mult max/unset

|--------------|——–|---------X--------X------------|

current value: = (current + mod) * mult

value = (current + mod) * mult, starts at (base + mod) * mult
if min or max is None, there is no upper/lower bound (default)
if max is set to “base”, max will be equal ot base+mod
descs are used to optionally describe each value interval. The desc of the current value value can then be retrieved with .desc(). The property is set as {lower_bound_inclusive:desc} and should be given smallest-to-biggest. For example, for a skill rating between 0 and 10:

{0: “unskilled”,
1: “neophyte”, 5: “traited”, 7: “expert”, 9: “master”}
rate/ratetarget are optional settings to include a rate-of-change of the current value. This is calculated on-demand and allows for describing a value that is gradually growing smaller/bigger. The increase will stop when either reaching a boundary (if set) or ratetarget. Setting the rate to 0 (default) stops any change.

trait_type = 'counter'¶

default_keys = {'base': 0, 'descs': None, 'max': None, 'min': None, 'mod': 0, 'mult': 1.0, 'rate': 0, 'ratetarget': None}¶

static validate_input(cls, trait_data)[source]¶: Add extra validation for descs

property base¶

property mod¶

property mult¶

property min¶

property max¶

property current¶: The current value of the Trait. This does not have .mod added and is not .mult-iplied.

property value¶: The value of the Trait. (current + mod) * mult

property ratetarget¶

percent(formatting='{:3.1f}%')[source]¶

Return the current value as a percentage.

Parameters

formatting (str, optional) – Should contain a format-tag which will receive the value. If this is set to None, the raw float will be returned.

Returns

float or str –

Depending of if a formatting string: is supplied or not.

reset()[source]¶: Resets current property equal to base value.

desc()[source]¶

Retrieve descriptions of the current value, if available.

This must be a mapping {upper_bound_inclusive: text}, ordered from small to big. Any value above the highest upper bound will be included as being in the highest bound. rely on Python3.7+ dicts retaining ordering to let this describe the interval.

Returns

str –

The description describing the value value.: If not found, returns the empty string.

class evennia.contrib.rpg.traits.traits.GaugeTrait(trait_data)[source]¶

Bases: evennia.contrib.rpg.traits.traits.CounterTrait

Gauge Trait.

This emulates a gauge-meter that empties from a (base+mod) * mult value.

min/0 max=(base+mod)*mult

|-----------------------X---------------------------|: value

= current

min defaults to 0
max value is always (base + mod) * mult
.max is an alias of .base
value = current and varies from min to max.
descs is a mapping {upper_bound_inclusive: desc}. These
are checked with .desc() and can be retrieve a text description for a given current value.

For example, this could be used to describe health values between 0 and 100:

{0: “Dead”
10: “Badly hurt”, 30: “Bleeding”, 50: “Hurting”, 90: “Healthy”}

trait_type = 'gauge'¶

default_keys = {'base': 0, 'descs': None, 'min': 0, 'mod': 0, 'mult': 1.0, 'rate': 0, 'ratetarget': None}¶

property base¶

property mod¶

property mult¶

property min¶

property max¶: The max is always (base + mod) * mult.

property current¶: The current value of the gauge.

property value¶: The value of the trait

percent(formatting='{:3.1f}%')[source]¶

Return the current value as a percentage.

Parameters

formatting (str, optional) – Should contain a format-tag which will receive the value. If this is set to None, the raw float will be returned.

Returns

float or str –

Depending of if a formatting string: is supplied or not.

reset()[source]¶: Fills the gauge to its maximum allowed by base + mod

Table of Contents

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evennia.contrib.rpg.traits.traits¶

Installation¶

Traits with TraitHandler¶

TraitProperties¶

Using traits¶

Trait types¶

Static trait¶

Counter¶

.descs¶

.rate¶

.percent()¶

Gauge¶

Trait¶

Expanding with your own Traits¶