---
id: flexparser
version: "0.4"
license: BSD-3-Clause
license_treatment: permissive
maintenance: dormant
---

# flexparser — Parsing made fun ... using typing.

License: permissive · Maintenance: dormant · Downloads: 5.7M/mo

## What it is and what it does

flexparser is a parser framework that lets you define custom statement types as frozen dataclasses with a `from_string` classmethod. Instead of writing a traditional recursive-descent or grammar-based parser, you write one class per statement type and the framework handles iteration, error collection, and file I/O. Each parsed statement is automatically annotated with line and column positions, raw text, and a content hash.

The framework distinguishes between statements the parser doesn't recognize (returns None), valid statements, and parsing errors (subclasses of ParsingError). It also supports grouping statements into blocks with begin/end markers. The result is a sequence of typed objects you can iterate over, making downstream processing type-safe and straightforward. It depends only on typing-extensions and requires Python 3.9 or later.

Use it for:

- Parse domain-specific languages or configuration formats where each line type maps to a distinct dataclass.
- Build error-tolerant parsers that collect all parsing failures and continue, reporting them at the end.
- Parse structured text files (logs, reports, DSLs) where you want position tracking and type safety without writing a grammar.
- Validate and extract data from line-oriented text where different line patterns need different handling logic.

## Worth the install?

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

flexparser lets you build parsers by writing dataclasses with a `from_string` method, automatically handling file parsing, error reporting, and structured output with type safety.

Yes, if you need a lightweight, type-safe parser for line-oriented text and don't require active maintenance. The low dependency footprint and permissive license make it a reasonable choice for small-to-medium parsing tasks. The dormant status means no new features or bug fixes are likely, so evaluate whether the current API and behavior meet your needs before committing.

## Install

pip install flexparser
uv add flexparser
poetry add flexparser

## Installing flexparser

Before you install: Low friction: pure Python wheel with only typing-extensions as a runtime dependency. Maintenance is dormant—last release was 2024-11-07 and last commit 2024-11-09, with no recent activity; the package is stable but not actively developed.

License in practice: BSD-3-Clause is permissive and imposes no significant restrictions on use or redistribution, making it suitable for most commercial and open-source projects.

Quickstart:

pip install flexparser

from dataclasses import dataclass
import flexparser as fp

@dataclass(frozen=True)
class Assignment(fp.ParsedStatement):
    lhs: str
    rhs: str
    
    @classmethod
    def from_string(cls, s):
        if "<-" not in s:
            return None
        lhs, rhs = s.split("<-")
        return cls(lhs.strip(), rhs.strip())

parsed = fp.parse("file.txt", Assignment)
for statement in parsed.iter_statements():
    print(statement)

Verify before relying:

- Whether the package handles nested or recursive block structures beyond the single-level Block example shown.
- Performance characteristics when parsing large files or deeply nested structures.
- Whether custom error recovery or partial parsing is supported beyond returning None or a ParsingError.

## Package facts

- License: BSD-3-Clause (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: dormant
- Downloads: 5.7M/month (top 5,000 on PyPI)
- Known vulnerabilities: none known

## Tags

dataclass-based parser, typed parsing framework, line-by-line file parser, parsing with type hints, structured text parsing, error-aware parser builder, statement parsing library, dataclass-parser, type-safe-parsing

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