Arpeggio
Packrat parser interpreter
Decision gist · record as of 2026-08-14
Yes. Arpeggio is a stable, actively maintained parser library with no dependencies and permissive licensing. Install it if you need to build a parser for a custom grammar or language; if you want a higher-level interface for language definition, consider textX instead.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Low install friction with no runtime dependencies.
- Active maintenance with a recent release in 2025-09-12 and last commit on 2026-08-02; the repository is not archived and has 288 stars.
License · maintenance · safety
MIT (permissive) — MIT license is permissive, allowing use in commercial and proprietary projects with minimal restrictions beyond attribution.
last release 2025-09-12 (336 days) · last repo commit 2026-08-02 · 288 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 2,075,233 downloads/mo, #3,316 on PyPI
Alternatives
Verify before relying
pip install arpeggio
from arpeggio import ParsingExpression, ZeroOrMore, OneOrMore, Optional
from arpeggio import PTNodeVisitor, visit_parse_tree
# Define a simple grammar and parse input
grammar = OneOrMore(ParsingExpression(...))
parse_tree = grammar.parse(input_string)- Whether Arpeggio handles left-recursive grammars or has known limitations with certain PEG patterns
- Performance characteristics when parsing large inputs or deeply nested structures
- Whether the package includes built-in error recovery or reporting mechanisms
What it is and what it does
Arpeggio is a parser library that implements Packrat parsing using Parsing Expression Grammars (PEG). It uses recursive descent with memoization to parse input according to user-defined grammar rules. The library is designed for developers who need to build parsers for domain-specific languages, configuration formats, or other structured text without writing hand-coded parsing logic.
The package has no runtime dependencies and is marked as Production/Stable. It supports Python 3.6 through 3.10 and has been actively maintained since its first release in 2014-08-16. The documentation notes that textX provides a higher-level interface to Arpeggio if you need a more convenient API for language definition.
Use it for
- Build a parser for a custom configuration file format or domain-specific language
- Parse structured text data where you want to define grammar rules declaratively rather than write parsing code
- Create an interpreter or compiler frontend that needs to consume and validate input against a formal grammar
- Extract and transform data from text files with complex, nested structures
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes.
Arpeggio is a stable, actively maintained parser library with no dependencies and permissive licensing. Install it if you need to build a parser for a custom grammar or language; if you want a higher-level interface for language definition, consider textX instead.
Install
arpeggio on PyPI
Before you install
Low install friction with no runtime dependencies. Active maintenance with a recent release in 2025-09-12 and last commit on 2026-08-02; the repository is not archived and has 288 stars.
License in practice
MIT license is permissive, allowing use in commercial and proprietary projects with minimal restrictions beyond attribution.
Quickstart
pip install arpeggio
from arpeggio import ParsingExpression, ZeroOrMore, OneOrMore, Optional
from arpeggio import PTNodeVisitor, visit_parse_tree
# Define a simple grammar and parse input
grammar = OneOrMore(ParsingExpression(...))
parse_tree = grammar.parse(input_string)Verify before relying
- Whether Arpeggio handles left-recursive grammars or has known limitations with certain PEG patterns
- Performance characteristics when parsing large inputs or deeply nested structures
- Whether the package includes built-in error recovery or reporting mechanisms
Package facts
| License | MIT permissive |
| Python support | Not specified |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Actively maintained 336 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 2,075,233 / month, #3,316 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableIntended Audience :: DevelopersIntended Audience :: Information TechnologyIntended Audience :: Science/ResearchLicense :: OSI Approved :: MIT LicenseOperating System :: OS IndependentProgramming Language :: Python :: 3Programming Language :: Python :: 3.10Programming Language :: Python :: 3.6Programming Language :: Python :: 3.7Programming Language :: Python :: 3.8Programming Language :: Python :: 3.9Topic :: Software Development :: CompilersTopic :: Software Development :: InterpretersTopic :: Software Development :: Libraries :: Python Modules |
Evidence: Arpeggio-2.0.3-py2.py3-none-any.whl
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See also TatSu · textparser · textX · parsimonious · funcparserlib · parsy · PyMeta3 · pyPEG2 · mo-parsing · Parsley