---
id: cfgv
version: "3.5.0"
license: MIT
license_treatment: permissive
maintenance: active
---

# cfgv — Validate configuration and produce human readable error messages.

License: permissive · Maintenance: active · Popularity: top 1,000 on PyPI

## Install

pip install cfgv
uv add cfgv
poetry add cfgv

## Description

[![build status](https://github.com/asottile/cfgv/actions/workflows/main.yml/badge.svg)](https://github.com/asottile/cfgv/actions/workflows/main.yml)
[![pre-commit.ci status](https://results.pre-commit.ci/badge/github/asottile/cfgv/main.svg)](https://results.pre-commit.ci/latest/github/asottile/cfgv/main)

cfgv
====

Validate configuration and produce human readable error messages.

## Installation

```bash
pip install cfgv
```

## Sample error messages

These are easier to see by example.  Here's an example where I typo'd `true`
in a [pre-commit](https://pre-commit.com) configuration.

```
pre_commit.clientlib.InvalidConfigError:
==> File /home/asottile/workspace/pre-commit/.pre-commit-config.yaml
==> At Config()
==> At key: repos
==> At Repository(repo='https://github.com/pre-commit/pre-commit-hooks')
==> At key: hooks
==> At Hook(id='flake8')
==> At key: always_run
=====> Expected bool got str
```

## API

### `cfgv.validate(value, schema)`

Perform validation on the schema:
- raises `ValidationError` on failure
- returns the value on success (for convenience)

### `cfgv.apply_defaults(value, schema)`

Returns a new value which sets all missing optional values to their...

## AI interpretation — verify before relying

cfgv validates configuration data structures and produces human-readable error messages that pinpoint exactly where validation failed, with support for nested maps, arrays, and conditional validation rules.

Verdict: cfgv is a lightweight, well-maintained validation library with zero dependencies, permissive licensing, and no known vulnerabilities. It is suitable for projects needing schema-driven configuration validation with detailed error reporting.

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