---
id: mo-parsing
version: "8.694.25301"
license: MIT
license_treatment: permissive
maintenance: aging
---

# mo-parsing — Another PEG Parsing Tool

License: permissive · Maintenance: aging · Downloads: 227.1K/mo

## What it is and what it does

mo-parsing is a fork of pyparsing optimized for faster parsing of PEG (Parsing Expression Grammar) languages. You define a grammar by combining predefined parser elements (Word, Literal, etc.) using Python operators, then call parse_string() to parse input text. The result is a ParseResults object that behaves like both a nested list and a dictionary, depending on how you named the matched elements.

The package emphasizes speed through regex-based optimization and faster infix operator parsing, and introduces a Whitespace context manager to control what characters are skipped and how the grammar behaves globally. It differs from pyparsing in that ParserElements are immutable—calling add_parse_action() returns a new element rather than modifying the original—and it removes backward-compatibility cruft. The main dependencies are mo-dots and mo-future, both lightweight utility packages.

Use it for:

- Parse domain-specific languages (DSLs) or configuration file formats into structured data
- Build SQL or query parsers where infix operator precedence matters
- Extract and transform text with named capture groups into dictionaries for downstream processing
- Define grammar rules for log parsing or protocol message decoding
- Implement expression evaluators that need to respect operator precedence

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

mo-parsing is a PEG parser generator that lets you define grammars using Python operators and predefined patterns, then parse strings into structured parse trees accessible as lists or dictionaries.

Yes, if you need a PEG parser and are comfortable with immutable ParserElement semantics. The low install friction, permissive MIT license, and lack of known vulnerabilities make it safe to try. The 290-day release gap suggests stability but not active development; use it for parsing tasks where pyparsing's API or performance is a concern, but verify performance gains match your use case before committing to a migration.

## Install

pip install mo-parsing
uv add mo-parsing
poetry add mo-parsing

## Installing mo-parsing

Before you install: Low install friction with only two runtime dependencies (mo-dots, mo-future). The package is in Beta status and has not seen a release in 290 days, suggesting stable but not actively developed maintenance.

License in practice: MIT license is permissive, allowing commercial and private use with minimal restrictions—you may use and modify this package freely provided you retain the license notice.

Quickstart:

pip install mo-parsing

from mo_parsing import Word
from mo_parsing.utils import alphas

greet = Word(alphas)("greeting") + "," + Word(alphas)("person") + "!"
result = greet.parse_string("Hello, World!")
print(dict(result))  # {'greeting': 'Hello', 'person': 'World'}

Verify before relying:

- Whether performance improvements over pyparsing are significant enough to justify migration for typical use cases
- How well the package handles complex or deeply nested grammars in practice
- Community size and availability of third-party examples beyond the repository

## Package facts

- License: MIT (permissive)
- Python support: unspecified
- Install friction: low
- Maintenance: aging
- Downloads: 227.1K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

PEG parser generator, grammar definition with operators, parse string to tree, pyparsing fork, language parsing library, text parsing DSL, infix operator parsing, parser-generator, peg-parsing, dsl

[View on SkillFed](https://skillfed.io/packages/mo-parsing) · [View on PyPI](https://pypi.org/project/mo-parsing/)