wadler-lindig

What it is and what it does

Wadler–Lindig is a pretty-printer for Python objects that implements the Wadler–Lindig algorithm, a layout algorithm that breaks lines more intelligently than the built-in pprint module. Instead of pprint's right-aligned continuation style, it produces vertically compact output that respects a target width and indentation level. The library has zero dependencies and is implemented in pure Python.

It is designed for two main use cases: replacing pprint in error messages and debug output where horizontal space matters, and creating custom pretty-printed representations for complex types like nested dataclasses or other tree-like structures. You can customize formatting either by adding a `__pdoc__` method to your class or by passing a `custom` formatter to the pprint call. It also supports ANSI escape codes and provides concise summaries for NumPy arrays and similar types.

Use it for:

• Format error messages and debug output that fit within terminal width constraints without excessive line wrapping.
• Create readable reprs for nested dataclasses or custom types by implementing the `__pdoc__` method.
• Display NumPy arrays in concise form (e.g., `f64[2,3](numpy)`) rather than full element dumps.
• Add ANSI escape codes to pretty-printed output for terminal-based debugging and logging.
• Replace pprint in test assertions or logging where output readability and compactness are both important.

Worth the install?

AI-flagged interpretation of the facts on this page — verify before relying

Formats Python objects for readable output using the Wadler–Lindig pretty-printing algorithm, which breaks lines more intelligently than the built-in pprint to consume less horizontal space.

Yes. It is a lightweight, dependency-free tool with active maintenance and no known vulnerabilities. Install it if you need better-formatted object output than pprint in error messages, debug logs, or custom repr implementations. The Alpha status is not a blocker—the algorithm itself is well-established—but be aware the API may change in minor ways before 1.0.

Install

wadler-lindig on PyPI

pip install wadler-lindig

uv add wadler-lindig

poetry add wadler-lindig

Installing wadler-lindig

Before you install

Low friction: pure Python with zero runtime dependencies, distributed as a wheel. Active maintenance with recent commits and no known vulnerabilities.

License in practice

Apache License 2.0 (permissive): you can use, modify, and distribute this code freely in commercial and private projects, provided you include a copy of the license and note any changes you make.

Quickstart

pip install wadler_lindig

import wadler_lindig as wl

obj = {"key": [1, 2, 3], "nested": {"x": "value"}}
wl.pprint(obj, width=30)

Requires Python 3.10 or later.

Verify before relying

• Whether the library handles all standard Python types (e.g., sets, frozensets, custom iterables) beyond the documented examples.
• Performance characteristics when formatting very large or deeply nested structures.
• Stability of the API given the 'Alpha' development status (0.1.7 version).

Package facts

Evidence: wadler_lindig-0.1.7-py3-none-any.whl

Keywords: leijen, lindig, pprint, pretty-printer, wadler

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