Piety is an operating system written in Python.
Motivation and Goals
Current Status
No Dependencies
Demos
Roadmap
Tested Platforms
Footnotes
Piety is a small but self-contained personal computer operating system for programmers. It provides a responsive and malleable platform for writing and programming. Its internals are easy to understand and modify.
Piety uses a single programming language -- Python -- for both the applications and the operating system. You can use the language interpreter to inspect and manipulate any data in the running system. Changes to application and system code are effective immediately, without having to stop and restart the system.
Piety is a reaction against the complexity and disempowerment of today's dominant computer systems. I take inspiration from the single user, single language, special hardware systems of the 1970s and 80s: Smalltalk, Lisp machines, Oberon (see doc/precursors.md). Piety is an experiment to see if I can put together something similar today, but using a familiar programming language running on ordinary hardware. Let's see how far we can get with just Python. There is already a lot of work by others that we might be able to adapt or use as models (see doc/utilities.md). For other projects in a similar spirit, again see doc/precursors.md.
For now, Piety runs in an ordinary Python interpreter session in a single terminal on a host operating system. The Python interpreter with its runtime is the virtual machine where the Piety OS now runs, analogous to the QEMU virtual machine in many other operating system projects.
Piety provides a display editor, a customized Python interpreter that also acts as the system shell, a customized debugger, and its own web browser. The display editor can support multiple buffers and windows in the terminal, and also a region for the Python interpreter. The debugger can work in the interpreter region without disturbing window contents. Together these provide a minimal but self-contained programming environment within a single Python terminal session.
Piety development is self-hosted in this programming environment. Code is added and revised in a long-running Python session. Code is imported and reloaded into the session without restarting or losing work in progress. To make this possible we adopted a particular workflow and coding style.
Piety provides concurrency with a Python asyncio event loop. Tasks are implemented by Python coroutines or readers (event handlers) that run in an event loop.
Piety provides asyncio readers for its custom Python shell and its editor. These enable the shell and the editor to run without blocking in an event loop, so other tasks can run concurrently, as you type commands in the shell or edit text in the editor.
The editor is not just for creating text. Python commands including concurrent tasks can redirect their output to editor buffers and windows, so the editor can be used for data capture and animated display. We use it for experiments in tasking and concurrency where tasks update windows as we control their behavior by typing commands at the Python interpreter.
We also use the editor as our web browser. Downloaded web pages are stored and displayed in editor buffers.
Here is more about some Piety design decisions and their rationales.
The present version of Piety was started from scratch in February 2023. Its development is ongoing here in the rewrite branch of the Piety repository. An archive of the earlier version of Piety that was abandoned in January 2023 is here in the master branch and version1 tag. The rewrite branch is now the main branch; I will never merge it back into master.
The Piety system has no dependencies, other than Python itself, including a few standard library modules.
With no dependencies, it is easy to try out Piety. Just clone this Piety repository and use your system's built-in python (or python3) command to run the scripts. You do not need to set up any Python environment.
Some interactive demonstrations are described in pmacs_script.md and edsel_script.txt and pmacs_blocking.md and audoindent.md and breakpt.md. These pages give instructions so you can do the demos yourself.
A few of the demos are not very interactive, so can be run from scripts: pmacs_script.py and edsel_script.py.
We don't have any screenshots or animations of these demos. Honestly, there is not much to see -- it just looks like Emacs in a terminal. To gain any understanding, you have to read along in the those files and work through the demos yourself.
I hope someday to run Piety on a bare machine with no other operating system, but only a Python interpreter with minimal support.
Piety divides naturally into two independent parts: the hosted part and the native part. The hosted part can run in any Python interpreter. It includes the editors, shells, tasking, the programming environment, and any tools and applications we might write. The native part includes the Python interpreter itself, and the support needed to run the interpreter on the computer hardware. Almost any general-purpose operating system can serve as the support, but the goal is to replace that with a special-purpose operating system which is itself mostly written in Python.
All the work I have done so far, including the programming environment, is in the hosted part. I have researched several approaches to building the native part. I hope to begin soon.
The obvious first step is to configure a minimal Linux running Python as its process 1. This would provide a system that boots into a Python prompt and provides a Python-only system to the user and application programmer. This is all we need to perform the essential experiment to see if it is feasible to continue Piety development and other personal computing activities using only Python running Piety in the console, without depending on a host OS to provide a desktop with multiple windows, the system shell, and other utilities.
The Piety software has run on a MacBook Pro running Mac OS, a Lenovo Chromebook running Linux, and an HP laptop running Linux. Details in platforms.md.
The phrase "complexity and disempowerment" is from a posting by jl6
Revised Apr 2025