schema

Simple data validation library

schema Permissive license MIT Active ★ 2,945 v0.7.8 released 2025-10-11

Install

schema on PyPI

pip

pip install schema

uv

uv add schema

poetry

poetry add schema

Package facts

License	MIT (permissive)
Python support	not specified
Install friction	low — pure-Python wheel
Runtime dependencies	1 — contextlib2
Maintenance	actively maintained — 306 days since the last release
Last repo commit	2026-06-20
First released	2012-08-22
Popularity	one of the top 1,000 most-downloaded packages on PyPI (30-day window, as of 2026-08-13)
Known vulnerabilities	none known (OSV.dev, checked 2026-08-13)

Evidence: schema-0.7.8-py2.py3-none-any.whl

Keywords: schema, json, validation

Development Status :: 3 - AlphaLicense :: OSI Approved :: MIT LicenseProgramming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.6Programming Language :: Python :: 3.7Programming Language :: Python :: 3.8Programming Language :: Python :: 3.9Programming Language :: Python :: Implementation :: PyPyTopic :: Utilities

About schema

from the package's own PyPI description — quoted content, verbatim

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 &lt;= n &lt;= 99),
            Optional("gender"): And(
                str,
                Use(str.lower),
                lambda s: s in ("squid", "kid"),...

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AI interpretation — verify before relying

AI-generated interpretation of the package facts above; every digit, version, license, or vulnerability id it cites is grounded in the facts already shown on this page

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.

Installation is straightforward with low friction—a pure-Python wheel with only contextlib2 as a runtime dependency. The project maintains active status with recent releases and 2945 GitHub stars, though the last commit date (2026-06-20) appears anomalous and warrants verification.

Schema is licensed under MIT (permissive), meaning you can use, modify, and distribute it freely in both open-source and commercial projects with minimal restrictions.

Usage

pip install schema

from schema import Schema, And, Use, Optional, SchemaError

schema = Schema({"name": And(str, len), "age": And(Use(int), lambda n: 18 <= n <= 99)})
validated = schema.validate({"name": "Sue", "age": "28"})

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.

Needs verification

Clarify the 2026-06-20 last commit date—whether this is a data error or indicates actual future development
Confirm whether the package actively maintains Python 3.10+ support despite Development Status :: 3 - Alpha classifier

python data validation libraryschema validation json yamldict list validationdata structure validationconfig file validationtype checking validationjson schema validator