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An Event Driven Python Game Engine

Project description


PursuedPyBear, also known as ppb, exists to be an educational resource. Most obviously used to teach computer science, it can be a useful tool for any topic that a simulation can be helpful.

A Game Engine

At its core, ppb provides a number of features that make it perfect for video games. The GameEngine itself provides a pluggable subsystem architecture where adding new features is as simple as subclassing and extending System. Additionally, it contains a state stack of Scenes simple containers that let you organize game scenes and UI screens in a simple way.

The entire system uses an event system which is as extensible as the rest of the system. Register new values to existing event types, and even overwrite the defaults. Adding a new event system is as simple as calling Engine.signal with a new datatype. Instead of a publisher system the engine knows everything in its own scope and only calls objects with appropriate callbacks. The most basic event is Update and your handlers should match the signature on_update(self, update_event, signal).

Guiding Principles

Because ppb started to be a game framework great for learning with, the project has a few longterm goals:

Education Friendly

Non-technical educators should feel comfortable after very little training. While some programming knowledge is required, the ability to think in objects and responses to events allows educators to only focus on their lessons.

Idiomatic Python

A project built on ppb should look like idiomatic Python. It also should look like modern Python. As such, we often add new language features as soon as they're available, letting a new user always know ppb runs on the latest Python.

Object Oriented and Event Driven

ppb games are built out of instances of objects that inherit from EventMixin. Each object only has enough information to respond to the event provided, which always includes the current BaseScene. Because ppb doesn't have a master list of events, you can provide new ones simply to add more granular control over your game.

Hardware Library Agnostic

Because ppb strongly tries to be extensible and pluggable, each hardware extension can provide its own hooks to ppb, and you can nearly seamlessly switch between various Python libraries.


One of the maintainers put it best:

If it’s not fun to use, we should redo it

ppb is about filing off the rough edges so that the joy of creation and discovery are both emphasized. A new user should be able to build their first game in a few hours, and continue exploring beyond that.

Try it

Install ppb in the standard method:

pip install ppb

ppb provides a run function that makes it simple to start single screen games.

To make a very simple game, make a directory and add an image file called ship.png to it. Then add the following to a python file and run it.

import ppb

class Ship(ppb.BaseSprite):

    def on_update(self, update_event, signal):
        self.position += 0, -(4 * update_event.time_delta)

def setup(scene):
    scene.add(Ship(pos=(0, 3.5)))


ppb is guaranteed compatible with Python 3.6 or later.

Get Involved

The fastest way to get involved is to check out the ongoing discussions. If you're already using ppb feel free to report bugs, suggest enhancements, or ask for new features.

If you want to contribute code, definitely read the relavant portions of Contributing.MD

Change Log


We went for a smaller release, but we got a lot done for it only being a few months. The most important bits are that all of the input events are in! Some cool stuff includes sprites scaling automatically and a new way to move between scenes that uses the event system. That means the old method is officially deprecated.

New stuff:

  • MouseButton events
  • Key events
  • Add a title to the game window
  • Sprite scaling based on game unit size
  • Keycodes flags
  • New scene change mechanism that uses the event system

Changed stuff:

  • Scene defaults are now class attributes
  • Most Sprite defaults are now class attributes
  • Flags can now be type hinted properly
  • Scenes no longer infinitely respawn their child scenes if running is True.
  • Fixed an issue with the frame being different dimensions to the viewport.
  • Fixed a bug in the Camera.point_in_viewport function
  • Default pixel ratio is now 64:1 (64 pixels to 1 game unit)
  • New (better) run function
  • Other type hinting fixes

Removed stuff:

  • bb attribute removed from sprites

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