---
id: schema
version: "0.7.8"
license: MIT
license_treatment: permissive
maintenance: active
---

# schema — Simple data validation library

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

## Install

pip install schema
uv add schema
poetry add schema

## Description

Schema validation just got Pythonic 
===============================================================================

**schema** is a library for validating Python data structures, such as those
obtained from config-files, forms, external services or command-line
parsing, converted from JSON/YAML (or something else) to Python data-types.


.. image:: https://secure.travis-ci.org/keleshev/schema.svg?branch=master
    :target: https://travis-ci.org/keleshev/schema

.. image:: https://img.shields.io/codecov/c/github/keleshev/schema.svg
    :target: http://codecov.io/github/keleshev/schema

Example
----------------------------------------------------------------------------

Here is a quick example to get a feeling of **schema**, validating a list of
entries with personal information:

.. code:: python
    
    from schema import Schema, And, Use, Optional, SchemaError
    
    schema = Schema(
        [
            {
                "name": And(str, len),
                "age": And(Use(int), lambda n: 18 <= n <= 99),
                Optional("gender"): And(
                    str,
                    Use(str.lower),
                    lambda s: s in ("squid", "kid"),...

## AI interpretation — verify before relying

Schema provides lightweight, Pythonic validation of data structures (dicts, lists, tuples) against declarative schemas, with support for type checking, callable predicates, and data transformation via Use and Regex validators.

Verdict: Schema is a mature, well-maintained validation library suitable for production use. It has no known vulnerabilities, minimal dependencies, and a permissive MIT license. The pure-Python implementation and broad Python version support (3.6–3.11, PyPy) make it easy to integrate. The anomalous future-dated last commit should be clarified before critical deployments.

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