trailing-comma

Add and remove trailing commas in Python source files.

A minimal replacement for add-trailing-comma, built on tokenize-rt. No AST — walks the token stream directly.

The original only exposes file and stdin interfaces — no way to work on strings directly. Exposing fix_trailing_commas(source) as the core API makes it usable as a library and directly testable, which revealed a latent bug in the original's unhug re-indentation logic.

Install

pip install trailing-comma

For development (includes build and twine for publishing):

pip install -e ".[dev]"

Usage

Rewrite files in place:

trailing-comma file1.py file2.py

From stdin (no arguments):

echo "foo(
    a, b
)" | trailing-comma

As a library:

from trailing_comma import fix_trailing_commas

result = fix_trailing_commas(source)

What it does

• Adds trailing commas to multi-line calls, defs, imports, lists, dicts, sets, and tuples
• Removes trailing commas from single-line constructs (preserves single-element tuples)
• Unhugs content from braces and fixes closing brace indentation

What it skips

Generators, comprehensions, class bases, subscripts, parenthesized expressions.