PyBevy is in an early and experimental stage. The API is incomplete, subject to breaking changes without notice, and you should expect bugs. Many features are still under development.
Startup System
Demonstrates systems that run once at application startup.
Introduction
PyBevy systems can run on different schedules. Startup systems run exactly once when the app begins, while Update systems run every frame. This is useful for initialization logic like spawning entities or loading resources.
from pybevy.prelude import *Startup System
This function runs once when the app starts. It's the right place to spawn initial entities, set up resources, or print a welcome message.
def startup(commands: Commands) -> None:
print("App has started!")
commands.spawn(Camera3d())Update System
This runs every frame. Here we just print a dot to show the app is running.
_frame_count = [0]
def update() -> None:
_frame_count[0] += 1
if _frame_count[0] % 60 == 0:
print(f"Frame {_frame_count[0]}")Running the App
@entrypoint
def main(app: App) -> App:
return (
app
.add_plugins(DefaultPlugins)
.add_systems(Startup, startup)
.add_systems(Update, update)
)
if __name__ == "__main__":
main().run()Running this example
Use PyBevy's hot reload feature to run and develop this example. If you don't have PyBevy installed, check out the Quick Start guide.
The code will reload automatically when you make changes to the file.
From Python to Rust
Notice how the core concepts in the code—Commands, Assets, App, and Systems—are identical to the original Bevy example?
This is the power of pybevy! It lets you learn Bevy's powerful, data-driven architecture in friendly Python.
When your project grows and you're ready for maximum, native performance, you'll already know the concepts to start writing systems in Bevy Engine with Rust.