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Piety is a notional operating system to be written in Python. It is a response to this impulse:

Today's operating systems and applications are bloated and complicated. Let's start over, and create a complete system that is small, easy to understand, and fun to program. And, let's build it all in our favorite language!

We draw inspiration from the single-user, single-language, special-hardware systems of the 1970s and 80s: Smalltalk, Lisp machines, Oberon (see doc/ Piety is an experiment to see if we can achieve something similar today with Python, but running on ordinary hardware. (For other projects in a similar spirit, again see doc/ We aim to produce, in Python, a simple but self-contained personal computer operating system. We aim to see how far we can get with just Python. There is already a lot of work by others that we might be able to use or adapt (see doc/

For now, Piety runs in an ordinary Python interpreter session on a host operating system. An overview of its design appears here. We have a script that demonstrates many Piety features, described here. We plan to run Piety on a bare machine (or bare VM) with no other operating system, but only a Python interpreter with minimal support. There are only a few platform-dependent modules. Most modules developed for Piety on a host operating system should also work on a bare machine.

Piety might be used for ---

  • Education - Exhibit and explain almost all of the code for an entire system, expressed in a readable high-level language (as they did for Oberon). Use the Python interpreter to inspect and manipulate any data structures in a running system.

  • Research - Experiment with new or unconventional operating system constructs (like the alternative to the file system proposed for LispOs).

  • Embedded computing - Run standalone Python applications on minimal platforms (something like PyMite or Micro Python).

  • Cloud computing - Run Python applications on virtual machines, minimizing resource consumption and startup time (as in Mirage, HalVM, Erlang on Xen, and OSv).

Another page describes the Piety directories and their contents.

An overview of the Piety design appears here.

A script that demonstrates many Piety features is described here.

Ongoing and recent work on Piety is described here.

The Piety system has no dependencies, other than Python itself (including a few standard library modules). This makes Piety a minimal self-contained system, written in a uniform style throughout. Alternatively, it might be possible to assemble similar functionality from other projects, but we expect the resulting system would be larger and harder to understand than Piety.

Piety is written in Python 3 since June 2015. Earlier work is saved in this repository in the python2 tag. The conversion is described here.

Revised Mar 2019

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