How can I store lists & dictionaries in an object?

Question

In blender, you can store strings, integers, floats, timers, and boolean operators in an object by creating a property in its logic. However, you cannot store lists and dictionaries. I am creating a class, and I can't store a dictionary or a list as you cannot create this in an object's properties. The only method I can seem to think of is the following:

• Have a module with the properties you want to save. For this example, I will refer to this module as class_properties.py.
• When creating the class, refer to class_properties.py for properties.
• In the module that has the class, use import imp and imp.reload(class_properties) in order to always reload the module and get the newest values.

Sure, this may work, but it's messy and nonsensical. With all my properties in my class, I can refer to the game object's properties. For example, I can do the following:

class Player(object):

    def __init__(self, game_object):
        self.game_object = game_object

        self.health = self.game_object["health"]

But if I have a dictionary, I cannot do the following:

class Player(object):

    def __init__(self, game_object):
        self.game_object = game_object

        self.health = self.game_object["health"]
        self.dictionary = dictionary{}

Why can't I do this? Well, the reason I used self.health = self.game_object["health"] is so I can update the player's game object's property health and have the class always have the updated value. If I use self.dictionary = dictionary{}, I would not be able to change dictionary according to the current scenario as self.dictionary would always be dictionary{} without anything in it as it always gets reset, for the __init__ function will always be called.

In other words, I need to have a dictionary in a game object's properties. I can store, for example, integers, in a game object's properties, so integers will always be stored. However, I cannot store a dictionary, so the class will never have the correct dictionary as it always gets reset in the __init__ function.

How can I store a dictionary & a list in a game object the same way I would store, for example, an integer? Thanks.

Answer 1

You can store anything in a game property from python. You simply assign it:

obj['inventory'] = {'sword':3, 'armour':5}

It doesn't have to be present in the logic brick window.

---

Also, you can (and probably should) store the instance of your class rather than regenerate it each frame. You can do this in a number of ways including:

• Using module mode and a global variable
• Saving it in a game property
• Saving it to bge.logic.globalDict

That way, __init__() isn't called every frame

---

The other thing you can do is you can mutate the game object. The API includes this example:

import bge

class CustomGameObject(bge.types.KX_GameObject):
    RATE = 0.05

    def __init__(self, old_owner):
        # "old_owner" can just be ignored. At this point, "self" is
        # already the object in the scene, and "old_owner" has been
        # destroyed.

        # New attributes can be defined - but we could also use a game
        # property, like "self['rate']".
        self.rate = CustomGameObject.RATE

    def update(self):
        self.worldPosition.z += self.rate

        # switch direction
        if self.worldPosition.z > 1.0:
            self.rate = -CustomGameObject.RATE
        elif self.worldPosition.z < 0.0:
            self.rate = CustomGameObject.RATE

# Called first
def mutate(cont):
    old_object = cont.owner
    mutated_object = CustomGameObject(cont.owner)

    # After calling the constructor above, references to the old object
    # should not be used.
    assert(old_object is not mutated_object)
    assert(old_object.invalid)
    assert(mutated_object is cont.owner)

# Called later - note we are now working with the mutated object.
def update(cont):
    cont.owner.update()

Which gives the game object the function 'update'