Awesome

commonast

A common AST description for Python

The aim of this project is to define a common ast description, that is the same for different Python versions and implementations. All code is in commonast.py. It defines a function parse() to act as a replacement for ast.parse().

For a definition of the nodes see the nodes docs.

Requirements / support

Commonast has been tested to work on:

• CPython 2.7
• CPython 3.3
• CPython 3.4
• CPython 3.5
• CPython 3.6
• CPython 3.7
• CPython 3.8
• pypy, pypy3, pypy4

Installation

Copy the commonast.py module to your own project or put it somewhere on your PYTHONPATH.

This module does not live on pypi and cannot be installed with pip. The reason for this is that the ast definition may need to be changed if new Python versions will be supported, which makes that we cannot guarantee backward compatibility.

Purpose

I'm using this in pscript so that the code there can be agnostic about Python version and implementation. Also, if me or someone else creates a pure Python AST parser that produces commonast, then we can easily use it in PScript to allow it to compile itself (which would open up some awesome possibilities).

The module is maintained from the Flexx project for now. That may change if commonast becomes used in other projects.

Maybe this project can be useful to others as well. I'd be happy to support making this more generally useful.

Related projects

• https://greentreesnakes.readthedocs.org provide the missing docs on Python's ast module. I found this a crucial resource when implementing commonast
• https://github.com/Psycojoker/baron
• https://github.com/davidhalter/jedi
• Python's buildin ast module (a C implemantation)
• Pythons buildin lib2to3 module (probably the easiest route for a pure Python ast parser.
• Some people are discussing a unified ast parser