Show HN: Python Source Code Refactoring Toolkit via AST

• prefactor

  1 12 0.0 Python

  Tool for writing Python refactorings

Nice, I've always thought Python could do better by adopting source transformation tools like babel. I implemented something similar using lib2to3, which preserves whitespace and comments more accurately: https://github.com/banga/prefactor

• hpy

  20 1,005 8.2 Python

  HPy: a better API for Python

  

Projects that depend on CPython C extensions should consider migrating to HPy[1] for C extension compatibility across Python implementations.

[1] https://github.com/hpyproject/hpy

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• Bowler

  4 1,513 0.0 Python

  Safe code refactoring for modern Python.

  

A similar type project. Though I haven't seen much activity recently:

https://github.com/facebookincubator/Bowler

• prosodia

  1 1 0.0 Python

  Parse Backus-Naur form syntaxs into parsers to generate ASTs of arbitrary syntaxs.

I wrote a library that takes a language specification (BNF, ABNF, etc) into a custom AST in Python. Then you can define a set of visitors for the custom AST to transform the tree into whatever you want. I implemented some checks integrated into the Python type system to type-check the visitors and I've used the library to do some non-trivial manipulations before.

It's mostly a pet project and I just wanted to share since it could maybe at least inspire something.

https://github.com/chrisphilip322/prosodia

• refactor

  7 434 0.0 Python

  AST-based fragmental source code refactoring toolkit for Python

Indeed! I also would suggest people to use a CST implementation (parso / LibCST) instead of refactor if they intend do large scale refactors, but from what I can see in my previous attempts (e.g teyit, a unittest assertion formatter) when you deal with small code fragments (a single expression, or a small statement) then you generally don't need to worry much about the style. The only concern is the literals (especially strings, which there are a few different variations of the same AST) where you could resurrect them back from the token stream (which the CustomUnparser representative in refactor allows).

The real start point for this project was to find / replace all type()'s in CPython codebase with type(type()) (e.g type('') would become type(str)) which is very light weight transformation, and I was able to write a script which did it without having any major problems about style on over 2000 files. Here it is for the reference: https://github.com/isidentical/refactor/blob/master/examples...

Also one thing to note here is that; in the last couple of years, thanks to black (and yapf), the adoptance of code formatters have really increased which is very nice for custom refactoring tools like refactor since the end-code would be refactored anyways so that means if you convert a multi line call, or a list to a single line version then the formatter you use probably reformat that segment anyways.

But thanks for authoring Bowler! It is a very cool project.

• semgrep

  74 9,724 9.9 OCaml

  Lightweight static analysis for many languages. Find bug variants with patterns that look like source code.

  

Maybe something like this:

https://semgrep.dev/

I found it last week. It may be able to detect a potential issue in multiple languages, but not sure if it supports refactoring.

• py2js

  1 3 2.7 Python

Nice! I like the syntax, this reminds me of the structural search and replace feature from IntelliJ IDEA. Is this the project you were referring to?

https://github.com/erezsh/py2js

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