---
id: wadler-lindig
version: "0.1.7"
license: Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. Definitions. "License" shall mean the terms and conditions for… (full text in the JSON record)
license_treatment: permissive
maintenance: active
---

# wadler-lindig — A Wadler–Lindig pretty-printer for Python.

License: permissive · Maintenance: active · Downloads: 4.9M/mo

## 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 above — 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

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

- License: Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. Definitions. "License" shall mean the terms and conditions for… (full text in the JSON record) (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 4.9M/month (top 5,000 on PyPI)
- Known vulnerabilities: none known

## Tags

pretty printer for python objects, wadler lindig algorithm, compact pprint alternative, custom repr formatting, nested dataclass pretty printing, ansi color pretty print, space-efficient object formatting, pretty-printing, debugging, formatting

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