https://github.com/true-grue/peco

Tiny parser combinators library written in Python.
https://github.com/true-grue/peco

minmalist parser-combinators peg python

Last synced: about 1 month ago
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Tiny parser combinators library written in Python.

• Host: GitHub
• URL: https://github.com/true-grue/peco
• Owner: true-grue
• License: mit
• Created: 2024-02-29T10:20:20.000Z (almost 2 years ago)
• Default Branch: main
• Last Pushed: 2025-05-20T21:39:35.000Z (8 months ago)
• Last Synced: 2025-08-25T21:05:28.530Z (5 months ago)
• Topics: minmalist, parser-combinators, peg, python
• Language: Python
• Homepage:
• Size: 41 KB
• Stars: 15
• Watchers: 3
• Forks: 4
• Open Issues: 3
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# peco

This is a tiny (100 LOC) parser combinator library in Python.

Installation:

```

pip install pecolib

```

Main features:

* Combined lexical and syntactic parsing using the PEG formalism.

* Lexical rules with regular expressions (see `eat`).

* Stack-based implementation of semantic actions (see `push` and `to`).

* Selective memoization for performance (see `memo`).

* Support for left recursion (see `left`).

Parsers are built from combinators and operate on a `Peco` namedtuple:

* `text: str`. Source text.

* `pos: int`. Position in the `text`.

* `ok: bool`. Parsing result.

* `stack: tuple | None`. Semantic result stack.

* `glob: dict`. Global data, including the error position field (`err`).

Most combinators follow PEG constructs:

* `empty`. Empty string.

* `seq`. Sequence.

* `alt`. Ordered choice.

* `many`. Zero-or-more.

* `some`. One-or-more.

* `opt`. Optional.

* `peek`. And-predicate.

* `npeek`. Not-predicate.

Support for semantic actions:

* `push(f)`. Pushes a text fragment parsed by the `f` combinator onto the `stack`.

* `to(f)`.  Pops `n` elements from the `stack` and passes them as arguments to function `f` with arity `n`. The result is pushed back onto the `stack`.

* `group(f)`. Combines all elements pushed onto the `stack` by `f` into a single tuple.

For examples of using peco's combinators, see the tests.