Pigframe

日本語版 README

Pigframe is a minimum ECS (Entity Component System) library for any Python-based game dev project. While I think it's quite rare to want to adopt ECS for game development in Python, I created this library because there wasn't an open-source library (at the time I started development) that provide both ECS and scene manager features in a single package.

I believe there are quite a few independent developers who would appreciate a framework with these features:

Key Features:

• ECS (Entity Component System) library that manages all game elements as integer object IDs and data, allowing for complete separation of logic. This module is compatible with any other game engines. Using witn Python friendly game engines is recommended.
• Reasonably Functional Scene Manager that exists as a separate system
• Provide Abstraction layer that handles engine-dependent physics systems

These features combined can make game development significantly more manageable for individual developers.

Getting Started:

To get started with Pigframe, simply install the pigframe from PyPI. Pigframe has no dependencies.

pip install -U pigframe # pigframe has no dependencies.

How to use:

• import module

  from pigframe import World, System, Event, Screen, Component

• create your own world class which manage entities, components, systems, events and screens. It is the start of your game scripts.

  # Implement World class for your own project.
  # Example 
  class App(World):
      def __init__(self):
          super().__init__()
          self.init() # write initial process which is unique to the game engine and the game you develop.
      
      ... # other game engine unique methods.
  
  app = App()

• create and remove entity

  # Create entity to world.
  entity = app.create_entity() # -> int: entity ID
  # Remove entity from world.
  app.remove_entity(entity) # deletes from entites list

• add/remove components to entity

  • add components to entity

    # Add component to entity ID.
    # Components are recorded as values where entity ID is the key inside dict.
    # Component instance are created automatically.
    app.add_component_to_entity(entity, ComponentA, **component_args) # ComponentA is not an instance of Component but type.
    app.add_component_to_entity(entity, ComponentB(**component_args)) # This is wrong way of use.
    # getter
    app.get_component(ComponentA) # Returns the list of tuple: entity id which has ComponentA, component object. -> list((int, ComponentA object))
    app.get_components(ComponentA, ComponentB) # Returns the list of tuple: entity id which has ComponentA and ComponentB, component objects.  -> list((int, (ComponentA object, ComponentB object)))

  • remove components from entity

    app.add_component_to_entity(ent, ComponentA, **component_argsA)
    app.add_component_to_entity(ent, ComponentB, **component_argsB)
    app.remove_component_from_entity(ent, ComponentA) # remove single component instance from entity
    
    app.add_component_to_entity(ent, ComponentC, **component_argsC)
    app.remove_components_from_entity(ent, ComponentB, ComponentC) # remove components instances from entity

• use component values inside system, event and screen

  # Example of using get_components() method.
  class SystemA(System):
      def process(self):
          for ent, (pos, vel) in self.world.get_components(Position, Velocity):
              """
              Update positions by velocity
              """
              pos.x += vel.x
              pos.y += vel.x

• use entity

  # Example of using entity object
  class EventA(Event):
      def __process(self):
          player = self.world.get_entity_object(0) # 0 is the entity ID
          """
          This method returns a dict
          -----------
          dict: entity object
              key: component type
              value: component
          """

• add scenes to world

  # Add scenes to world.
  app.add_scenes(["launch", "game", "result", "settings"])
  add.add_scene("game_over")
  # scenes getter
  app.sceneces # -> [["launch", "game", "result", "settings", "game_over"]

• add/remove system to/from world

  # Add screen to a scene of world. Be sure you have added scenes before adding systems.
  # System instance are created automatically.
  app.add_system_to_scenes(SystemA, "launch", priority = 0, **system_args)
  # system with its lower priority than the other systems is executed in advance., by default 0.
  # World calls System A then System B.
  app.add_system_to_scenes(SystemA, "game", priority = 0, **system_args)
  app.add_system_to_scenes(SystemB, "launch", priority = 1)
  # Remove system from scene.
  app.remove_system_from_scene(SystemA, ["launch", "game"])

• add/remove screens to/from world

  # Add screen to a scene of world. Be sure you have added scenes before adding screens.
  # Screen instance are created automatically.
  app.add_screen_to_scenes(ScreenA, "launch", priority = 0)
  app.add_screen_to_scenes(ScreenB, "launch", priority = 0)
  app.add_screen_to_scenes(ScreenC, "game", priority = 0, screen_args)
  # Remove screen from scene.
  app.remove_screen_from_scene(ScreenB, "launch")

• add/remove event to/from world

  # Add an event, event triger to a scene of world. Be sure you have added scenes before adding events.
  # Event instance are created automatically.
  app.add_event_to_scene(EventA, "game", callable_triger, priority = 0)
  # Remove event from scene.
  app.remove_event_from_scene(EventA, "game")

• add scene transitions settings

  app.add_scene_transition(scene_from = "launch", scene_to = "game", triger = callable_triger)
  # triger has to be callable.

• execute systems, events and draw screens

  # Example with Pyxel (Python retro game engine)
  class App(World):
      ...
  
      def run(self):
          pyxel.run(self.update, self.draw)
  
      def update(self):
          self.process() # World class has process method.
          # process method calls these internal methods below.
          # 1. process_systems()
          # 1. process_events()
          # 1. scene_manager.process()
  
      def draw(self):
          self.process_screens()

  In update() method, of course, you can customize execution order as well.

  def update(self):
    self.process_user_actions()
    self.process_systems()
    self.proces_events()
    self.scene_manager.process() # Pigframe implements scene listener and World class use this class to manage scenes.

  # Pygame Example
  class App(World):
      ...
      
      def run(self):
          while self.running:
              self.update()
              self.draw()
              
      def update(self):
          self.process()
      
      def draw(self):
          self.process_screens()

when some components' parameters are entity_id and you want to load saved data which had been created by the previous game, you can put entity_id to create_entity method and use set_next_entity_id method of World class to ensure the same entity_id represents the same game object between the previous game and the current game sessions.

## session1
a = world.create_entity() # -> 0
b = world.create_entity() # -> 1
c = world.create_entity() # -> 2
world.add_components_to_entity(c, Relation, friedns=[b])
## remove a
world.remove_entity(a)

## session2
max_entity_id = 0
for entity_id, data in loaded_data:
    world.create_entity(entity_id=entity_id) # ensure the same entity_id represents the same game object between sessions.
    for component_name, component_data in data["components"].items():
        component_class = globals()[component_name]
        world.add_component_to_entity(entity_id, component_class, **component_data)
    max_entity_id = max(max_entity_id, entity_id)
... # after loading
world.set_next_entity_id(max_entity_id + 1) # prevent entity_id conflict

If you want to know the examples of real game project, please check micro projects listed below.

Examples

game engine	example	contents
Pyxel	2D shooting game	examples of system, event, component, entity and world implementations.
Pygame	control a ball	examples of system, event, component, entity and world implementations.
Pyxel	control a ball	examples of system, event, component, entity and world implementations.

Contributing:

Contributions to Pigframe are welcome! Whether it's bug reports, feature requests or code contributions, any inputs are valuable in making Pigframe better for everyone.