flow: A Python repository from darkf

Flow - a dynamic Entity-Component-System engine for Python

Overview

Components are just grab-bags of data. They're similar to the concept models you might be familiar with in other systems like MVC.

PositionComponent = Component(x=0, y=0)
VelocityComponent = Component(vx=0, vy=0)
SquareComponent = Component(size=30)

Here we define two components, just being containers for their attributes (a set of x and y positions, a vx and vy vector for velocity, and a size for defining a square.)

Entities are likewise just grab-bags of components - they also handle getting and setting attributes on components.

spaceship = Entity(PositionComponent, VelocityComponent(vx=1, vy=1), SquareComponent)

Now we have a spaceship that has a position, a velocity (heading to the bottom-right), and is a square. But it's all just data! We could print that data out:

>>> print(spaceship.size)
30

But what good is that if we can't do anything?

Systems are functions that accept an entity (possibly filtered by required components) as input and performs an operation on it. They're called every update tick, so they're useful for defining game and rendering logic.

# update every entity with a position and a velocity
@system(PositionComponent, VelocityComponent)
def physicsSystem(entity):
    entity.x += entity.vx
    entity.y += entity.vy

And we might want to render all squares with positions:

@system(PositionComponent, SquareComponent)
def squareRenderSystem(entity):
    drawRectangle(entity.x, entity.y, entity.size, entity.size)

Implementation

We provide an engine that uses pygame to power the graphics and timing. Using it is simple:

from flow import Entity, Component, system
from engine import PygameGame

# ...

if __name__ == '__main__':
    game = PygameGame(800, 600) # 800x600 window
    game.scene('main', [
        # systems
        physicsSystem, squareRenderSystem,
        # entities
        spaceship
    ])
    game.run()

And you're done.

darkf/flow

Overview

Implementation